Published for the Division of Materials Sciences, Office of Basic Energy Sciences, USDOE, under Contract W-7405-eng-82 with the Ames Laboratory, Iowa State University. Funded by DMS/BES/USDOE, ARPA/DOD, ONR/DOD, EPRI, NASA, and other agencies, organizations, and individuals.
--------------------------------------------------------------------- The e-mail version of the High-Tc Update is sent to e-mail addresses accessible over BITNET (including INTERNET addresses such as EDU, ARPANET, COM, etc.). You can send e-mail messages to the editor at MITRA@ALISUVAX.BITNET or MITRA@AMESLAB.GOV.
Please note, issues of High-Tc Update from November 15, 1993, onward are also available in coded Word versions (BINHEX and RTF). If you are interested in these versions, contact the editor for information.
---------------------------------------------------------------------
PLEASE READ: The electronic-mail version of High-Tc Update is generated from a Macintosh Microsoft Word file and turned into a text file that can be transferred electronically. Formatting commands, Greek symbols, diacritical marks, etc. are lost in this transformation. In order to improve the readability of the e-mail version, the newsletter staff add explanatory marks as needed to the text file. For example, a carat (10^5) indicates a superscript (ten to the fifth). A carat followed by a bracket (cm^[-2]) indicates everything within the brackets is superscripted (centimeter to the minus 2). A bracket followed by a carat ([18]^O) indicates everything before the carat is superscripted. An underline (M_i) indicates a subscript (M subscript i). Most Greek letters are spelled out (Delta, mu, tau, pi, Omega), although delta is left as "d." In most instances, easily recognizable formulas or units are left as they appear: Tc, Jc, YBa2Cu3O7, O2. Mu-m is changed to micrometers. Diacritical marks (accents, tildes, carats, etc.) are removed, but the German umlaut (e.g., a, o, or u with two dots over it) is changed into a, o, or u followed by e. If needed for clarity, hyphens are occasionally inserted between spelled-out Greek letters or symbols (ohm-cm, sin-theta).
---------------------------------------------------------------------
Correction: In our April 15 issue we discussed an experiment, reported by J. R. Kirtley (IBM-Yorktown) in a contributed paper at the March APS Meeting, showing only half-integral flux quanta in a three-junction superconducting YBa2Cu3O7-d ring. The conditions for the figure shown on p. 15 of that issue differed from those for the corresponding figure in the preprint, and our caption should have been: "FIG. 1. Scanning SQUID microscope image of four superconducting YBa2Cu3O7-d rings [see preprint by C. C. Tsuei et al. (IBM-Yorktown) and discussion in Nota Bene]. The center ring, with three grain-boundary junctions, has flux phi_0/2 threading it, while the other three rings, with zero or two grain-boundary junctions, have flux phi_0 (h/2e = superconducting flux quantum) threading them. The result is consistent with d-wave pairing symmetry."
Borocarbides
Muon (mu^+) spin relaxation measurements have been performed by D. W. Cooke (Los Alamos) et al. to investigate the coexistence of magnetism and superconductivity in TmNi2B2C and LuNi2B2C. The zero-field muon precessional frequency in TmNi2B2C is dominated by spin dynamics of the fluctuating Tm moments throughout the temperature range 1.4 K <= T <= 100 K, with the internal field sensed by the muon exhibiting a quasistatic component below 16.5 K. This component varies as T^[-1] from 16.5 K to a maximum value suggesting complete ordering at T = 2.5 K, the variation being continuous through the superconducting transition temperature Tc = 9.5 K. The muon relaxation rate scales roughly with this variation but exhibits an additional cusp-like feature at Tc. A contribution from Ni moments to the magnetic ordering at low temperatures cannot be excluded, and in LuNi2B2C (Tc = 15.3 K) the muon polarization results provide evidence for fluctuating atomic moments attributable to Ni for T <= 5.5 K. These moments order near T = 2 K.
The specific heat of single crystals of superconducting YNi2B2C and TmNi2B2C has been measured by R. Movshovich (Los Alamos) et al. Analysis of the YNi2B2C data in zero and 5 T magnetic fields indicates modestly strong electron-phonon coupling and a superconducting energy gap parameter Delta(0) = 29 K. In TmNi2B2C, superconductivity coexists with antiferromagnetic order below 1.5 K. The specific heat at very low temperature indicates substantial magnetic anisotropy, with ferromagnetic planes weakly coupled antiferromagnetically. Two-dimensional ferromagnetic spin waves produce a large linear-in-temperature contribution to the specific heat. The authors find no compelling evidence for unconventional pairing in these systems.
Specific-heat measurements also are reported by S. A. Carter (AT&T Bell Labs) et al. on LuNi2B2C and LaPt1.7Au0.3B2C in magnetic fields up to 7.7 T. For LuNi2B2C, which has Tc = 16.5 K, the authors find a large density of states at the Fermi level, gamma = 19(2) mJ/mole K^2, and an effective Debye temperature of Theta_D = 345 K. For LaPt1.7Au0.3B2C with Tc = 10.2 K, the corresponding values are gamma = 7.5(1.5) mJ/mole K^2 and Theta_D = 220 K. By comparing the specific heat anomaly at Tc, Delta C/[gamma-Tc], the magnetic susceptibility, and the calculated band structure, the authors conclude that these compounds are in the weak to intermediate coupling limit with lambda = 0.5-1.0. The position of these compounds on the gamma vs. Tc plot indicates predominantly phononmediated electron pairing.
Superconducting and structural properties of YNi2B2C are reported by N. M. Hong (T. U. Wien) et al. Magnetic and specific-heat measurements indicate type-II superconductivity with an onset Tc = 15.2 K and a specific-heat discontinuity Delta C/[gamma-Tc] = 1.57. The authors estimate for the upper critical field mu_0H_[c2](0) = 3.7 T, the coherence length xi_[GL] = 9.4 nm, and the Ginzburg-Landau parameter kappa = 1.5.
Superconductivity with Tc = 14.2 K in the compound YCo2B2C is reported by K. Ghosh (Tata-Bombay) et al. The authors find only a very small heat capacity jump at Tc. Another preprint by K. Ghosh et al. reports superconductivity in LuCo2B2C with Tc = 15.2 K and a specific-heat jump of 220 mJ/ mole K. The authors conclude that LuCo2B2C is a superconductor with intermediate electron-phonon coupling.
AxC60
A preprint by S. Sasaki (NTT) et al. reports on NMR studies of [13]^C in K3C60 at temperatures 35.3 K and 16.2 K above and below Tc with an applied field of 2.93 T. The authors find that the non-singleexponential recovery data can be fit by two components and normalized to the same shape at both temperatures. With the spin-lattice relaxation time T1 defined in this way, the authors identify Fermiliquid behavior above Tc and find that the broadened Hebel-Slichter peak below Tc can be explained by the Eliashberg theory with 2 Delta(0)/k_BTc = 4.31.
Hg Cuprates
Electronic structure and hole concentrations in the high-Tc superconductor HgBa2CaCu2O6+d have been carried out by B. K. Agrawal (Allahabad) et al. using a first-principles full potential selfconsistent linear-muffin-tin-orbital (LMTO) method with the localdensity-approximation (LDA) theory. When delta = 0, the calculations show that, with increasing pressure on the crystal, the hole concentration always increases, with no maximum or saturation value. On the other hand, the van Hove singularity peak in the density of states approaches the Fermi level with increasing pressure, and it is pinned at E_F for a range of crystal volumes V around V/V_0 = 0.77 (V_0 is the experimental volume at normal pressure), where the Fermi-surface nesting area becomes maximum.
YBa2Cu3O7-d
Frozen-phonon LDA calculations for YBa2Cu3O7 are reported by A. I. Liechtenstein et al. (MPI-Stuttgart). The authors investigated the infrared- and Raman-active apical-oxygen phonons in the c direction and found no sign of the suggested bistability or anharmonicity. The authors conclude that, if there is an apical oxygen bistability, this can only be due to strong correlation effects not included in the LDA.
A preprint by K. Conder (ETH Zurich) et al. reports measurements of the oxygen self-diffusion coefficient in the process of isotope exchange of chain sites in YBa2Cu3O7-d ( delta < 0.05). The authors find that the oxygen diffusion rate is large enough to assure a homogeneous oxygen distribution in grains of size 10-50 micrometer after annealing at about 320^oC for 200-300 h in oxygen. The authors thus conclude that the double superconducting transition observed by several authors cannot be explained by oxygen inhomogeneity in the grains of the material.
A sharp peak (20% of the normal resistivity), just above the superconducting transition, in the curve of the ab-plane electrical resistivity versus temperature rho_[ab](T) of some non-fully oxygenated YBa2Cu3O7-d crystals with transition temperatures Tc below 90 K is reported by J. Mosqueira et al. (Santiago). The peak amplitude decreases in an applied magnetic field perpendicular to the ab plane, and it is also affected by the electrical-contact configuration or by further re-oxygenation of the crystals. The authors offer an explanation in terms of Tc inhomogeneities associated with spatially inhomogeneous oxygen content.
The microstructural effects of CeO2 and Y2BaCuO5 (211) additions during melt texturing of YBa2Cu3O7-d are reported by C. J. Kim (Notre Dame) et al. The added CeO2 was converted to BaCeO3 of size smaller than 1 micrometer. Moreover, when 5wt% CeO2 was added, the 211 particle size was reduced to 2 micrometers regardless of the 211 content, but without CeO2 the 211 particle size was 8 micrometers in a sample with 20wt% 211 added. The results help to explain the report by N. Ogawa and H. Yoshida [Adv. Superconductivity IV, 455 (1991)] that CeO2 increases Jc in melt-textured samples by refinement of 211 particles.
A major impediment for many applications of bulk high-Tc superconductors is that grain-boundary weak links drastically limit their supercurrent-carrying ability. A. S. Parikh et al. (TCSUH) have developed a method to eliminate secondary phases and reduce microcracks at grain boundaries in YBa2Cu3O7-d superconductors by removing a fraction of the liquid phase formed during melt texturing. The processing conditions have been tailored to obtain YBCO domains of length 15-20 mm, width 8-10 mm, and thickness 5 mm with grain boundaries free of secondary phases and microcracks.
A seeded directional solidification method that allows the fabrication of long lengths of single-domain YBa2Cu3O7-d with large cross-sectional area and predetermined grain alignment has been developed by D. F. Lee et al. (TCSUH). The current-carrying capability of these superconductors is reported to be superior to that of misaligned ones, and the critical current at 77 K is estimated to be a few thousand amperes for samples of 4 x 8 mm^2 cross-sectional area.
Bi Copper Oxides
The effects of improved materials processing on single-BiO-layer cuprates in the (Bi,Pb)-Sr-(Ca,Y)-Cu-O system have been investigated by P. Zoller et al. (Tuebingen). The authors report Tc = 102 K in Bi-2212 with superconducting volume fractions of 30-40%. The magnetically determined critical current density (taking the length scale as the sample radius) was found to be 2 x 10^6 A/cm^2 at 5 K and 0 T. The authors also report evidence for Bi-1223 with a superconducting transition in the range 115-150 K.
A detailed synthetic effort to incorporate Y/RE (rare earths) into the (Bi,Pb)2Sr2Ca2Cu3O10+d (Bi-2223) phase is reported by P.V.P.S.S. Sastry et al. (Bhabha-Bombay). The authors report that, because of a combination of thermodynamic and kinetic factors, the 2223 phase is not stable in the presence of even small amounts of Y/RE. In all the attempts, the 2212 phase with Y/RE substituted for Ca was formed as the major phase. Even single-phase 2223 disappeared completely to give 2212 phase when reacted with Y/RE-containing materials. These results caution against the use of any Y/RE-based additives or substrates during the fabrication of Bi-2223 wires, tapes, or films.
Studies of the magnetization curves of high-quality superconducting Bi2Sr2CaCu2O8+d single crystals in fields parallel to the c axis are reported by A. K. Pradhan (Indore) et al. With decreasing temperature, the authors report a low-field anomaly in the magnetization at 25 K and a sharp rise of the irreversibility line and a nonlogarithmic magnetic relaxation. The authors argue that 25 K is a boundary temperature where the system undergoes a 2D to 3D dimensional crossover.
Tl Cuprates
The microstructure of high-critical-current-density (1.2 x 10^5 A/cm^2 at 77 K in 1 T) superconducting Tl1-yBa2Ca2Cu3Ox, y < 0.2, (Tl-1223) films grown on polycrystalline yttria-stabilized zirconia (YSZ) substrates has been investigated by E. D. Specht (Oak Ridge) et al. The results show that plate-like grains are aligned with their c axes normal to the film and that the a and b axes of grains separated by a few mm are randomly oriented. However, in regions of the sample with the highest critical current densities, only small-angle intergranular grain boundaries are present, and the a axes of the grains remain well aligned over distances up to 1 mm. To explain the critical current density, the authors propose a model in which the supercurrent flows along (001) planes through a percolative network of small-angle [001] tilt boundaries.
Vortices
Small-angle neutron scattering has been used by J. W. Lynn (NISTGaithersburg and Maryland) et al. to investigate the vortex lattice in single-crystal Nb. In the mixed state (H_[c1] < H < H_[c2]) a six-fold hexagonal pattern of peaks was observed at all temperatures. Below the irreversibility line these peaks were resolution-limited, but above it the width in the transverse direction increased with temperature because of the vortex dynamics. Near H_[c2] the radial widths also broadened. The basic hexagonal pattern of peaks was maintained throughout, indicating that a correlated flux liquid exists in the reversible regime.
Using an extended Ginzburg-Landau approach, V. V. Kurin and A. I. Panfilov (Nizhny Novgorod) have theoretically considered vortices and vortex lattices in superconductors with additional ordering, such as charge density waves or antiferromagnetism. The authors predict new vortex and vortex-lattice structures, and they find that the magnetization curves become hysteretic even in the absence of pinning centers.
A preprint by M. Boiko et al. (MPI-Stuttgart) considers the influence of various defects on vortices in high-Tc superconductors and estimates both the elementary pinning potential and the elementary pinning force of point defects (vacancies), one-dimensional defects (dislocations), two-dimensional defects (twin and low-angle boundaries), and three-dimensional defects (pores, precipitates, etc.).
Two preprints by V. D. Ashkenazy (Bar-Ilan) et al. consider random voltage noise during flux flow in superconductors carrying currents above the critical current. One preprint describes the theoretical model, while the other describes experiments in granular YBCO thinfilm strips.
Flux motion in anisotropic type-II superconductors near H_[c2] has been considered by Z. Hao (TCSUH) and C.-R. Hu (Texas A&M) using the time-dependent Ginzburg-Landau (TDGL) theory. The authors consider the case that the average flux density B is oriented in an arbitrary direction relative to the principal axes of the sample. The authors solve the linearized TDGL equation for a uniformly translating order parameter and obtain expressions for all the components of the fluxflow resistivity tensor rho_[ij], including the off-diagonal Hall elements. The theory explains (in the high-field region) several angular scaling properties. For example, the diagonal elements rho_[ii] show the scaling property that rho_[ii](B) = rho_[ii][B/H_[c2]( theta, phi)], while the Hall elements rho_[ij] (i not equal to j) have additional angular dependencies not contained in H_[c2]( theta, phi). The theory also accounts for the Lorentz-force independence of the in-plane longitudinal resistivity in high-Tc superconductors when B is nearly, but not exactly, parallel to the current density J and the ab plane. Expressions for the viscosity (viscous drag) tensor eta_[ij] also are obtained.
The voltage-current (V-I) characteristics of a YBa2Cu3O7-d single crystal have been measured by R. Busch et al. (Erlangen and Siemens) for currents both parallel and perpendicular to the broad face of the crystal. The authors note that the V-I characteristics for currents parallel to ab and to c are strikingly similar over the entire range of investigated fields (0.02 T - 7 T) and temperatures (80 K - 89 K). The authors therefore argue that the dominant voltage drop for both current directions arises from the same dissipative process, namely current transfer between adjacent CuO2 layers.
The role of vortices in triggering layer decoupling in the absence of applied magnetic fields has been studied theoretically by M. Friesen (Minnesota) for the case of anisotropic layered superconductors, such as the high-Tc cuprates. The author uses a phenomenological realspace renormalization group procedure to show that layer decoupling plays an essential role in the zero-field transition of a model layered system, and that it can be viewed as a bridge between 2D and 3D phenomena. The results also show why a quasi-2D model is so successful in explaining many experimental results in the hightemperature superconductors.
A real-space renormalization group study of the critical behavior of vortices interacting in zero field in a system of weakly coupled superconducting layers also has been done by S. W. Pierson (NRL). The author finds that the screening due to small intralayer pairs weakens the interlayer coupling and can be the dominating effect above Tc. This is consistent with the Monte Carlo studies of P. Minnhagen and P. Olsson [Phys. Rev. B 44, 4503 (1991); Phys. Rev. Lett. 67, 1039 (1991)], which implied that the system is 3D below Tc and 2D above.
Calculations of the current-voltage characteristics in a twodimensional Josephson-junction array have been carried out by T. J. Hagenaars (Utrecht) et al. The authors note that the results in the damped regime are well described by a model involving a nonlinear viscous drag force expressed in terms of a velocity-dependent viscous drag coefficient eta.
Collective Modes
Recent preprints by M. Tachiki et al. (see Jan. 1, 1994, issue) and by L. Bulaevskii et al. (see Mar. 15, 1994, issue) have considered plasmons and collective modes in layered superconductors. This issue contains several more papers on this topic; see the preprints by S. M. Bose (Drexel) et al., V. M. Gvozdikov (Kharkov), L. Z. Kon and I. P. Ciobanu (Kishinev), S. V. Pokrovsky (MIT) and V. L. Pokrovsky (Texas A&M and Landau Institute), A. C. Sharma and I. Kulshrestha (Jiwaji), and M. Tachiki et al. (Tohoku).
Surface Impedance
Surface impedance measurements at 60 GHz have been performed by O. Klein (UCLA) et al. on superconducting Nb and Pb. The experimental results on Nb are in good agreement with the BCS weak coupling theory, while the data on Pb can be accounted for only by the Eliashberg strong-coupling description of the electrodynamics of the superconducting state.
A preprint by H. A. Blackstead (Notre Dame) et al. reports measurements of the ab-plane surface resistance of YBa2Cu3O7-d films at temperatures several degrees below Tc. The contribution of fluxflow resistivity is identified by its dependence on temperature and on the angle between the induced currents and the applied dc field.
A theory of the surface impedance of a type-II superconductor in the mixed state, including the effects of a Bean-Livingston surface barrier, has been developed by E. B. Sonin and K. B. Traito (St. Petersburg).
Experimental results on the low-field microwave magnetoabsorption in granular samples of YBCO and BSCCO are discussed by S. M. Bhagat (Maryland). The results are interpreted using a weak-link model.
The development of a new technique for measuring the surface impedance of the mixed state of superconducting films over the frequency range 45 MHz - 20 GHz is reported in a preprint by J. C. Booth et al. (Maryland).
YBCO Films on Metallic Substrates
As stressed by R. Chatterjee et al. (NRIM), the development of methods for depositing high-Tc YBa2Cu3O7-d (Y-123 or YBCO) superconducting thin films on metallic substrates is technically important for such applications as superconducting magnets, cables, and electromagnetic shields. However, it is necessary that the Y-123 material be strongly oriented with its c axis normal to the substrate and that there be good surface morphology. It is now known that good-quality Y-123 films can be deposited on the Ni-based alloy, Hastelloy C-276, over a buffer layer of yttria-stabilized zirconia (YSZ). (The main constituents of Hastelloy are Ni and Cr.) Moreover, J. Saitoh et al. [Jpn. J. Appl. Phys. 30, L898 (1991)] and E. Narumi et al. [Appl. Phys. Lett. 58, 1202 (1991)] have shown that a thin (~20 nm) underlayer coating of Pt (under the YSZ) aids the caxis orientation, improves the film texture, and raises the transport critical current density Jc.
The preprint by R. Chatterjee et al. describes the preparation of biaxially aligned YSZ buffer layers on polished Hastelloy (HA) tapes of dimensions 3 x 50 x 0.3 mm^3 by a modified bias sputtering method. The authors report the effect of 20 nm underlayer coatings of Pt, Pd, Au, and Ag (M), prepared by an rf magnetron sputtering method. The YSZ layer thicknesses were in the range 0.5-0.7 micrometer. The authors examined the properties of laser-ablation-deposited Y-123 films in HA/M/YSZ/YBCO and HA/YSZ/YBCO multilayers. The authors found that all four of the underlayer metals were effective in improving the surface morphology and that Jc depended strongly on the percentage lattice mismatch between the YSZ buffer layer and the Y123 film's a-axis lattice parameter. The critical current density was strongly degraded when the percentage mismatch exceeded 4%.
Thin Films
An arrangement for large-area pulsed-laser deposition of YBCO thin films over YSZ buffer layers on three-inch r-plane sapphire wafers is described by M. Lorenz et al. (Leipzig). The resulting YBCO films had 90% Tc's in the range 85.9-86.7 K and 77 K critical current densities in the range 1-2 x 10^6 A/cm^2.
A preprint by M. G. Norton (Washington State) et al. describes a study of the surface morphology of YBa2Cu3O7 thin films grown on (001)-oriented LaAlO3 substrates by pulsed-laser deposition. The observed surface features are of two types: particles formed as a result of material (often molten) ejected from the target, and outgrowths formed as a result of nucleation and growth processes on the substrate and/or the film surface.
A comparison study of YBa2Cu3O7-d thin films deposited on LaSrGaO3 and LaAlO3 substrates has been done by A. W. McConnell et al. (McMaster). The LaSrGaO3 crystals were grown, cut, and polished inhouse, while the LaAlO3 substrates were prepared commercially. Growth temperatures above 780^oC on both substrates yielded highly oriented c-axis material with excellent transport properties. Because LaSrGaO3 has the advantage of being untwinned, a desirable property for microwave-device applications, the authors conclude that it has much promise as a potential substitute for LaAlO3.
Devices
Transient behavior and memory effects in a ferroelectric PZT [Pb(ZrxT1-x)O3] and superconducting YBCO (YBa2Cu3O7-d) three-terminal device have been investigated by H. Lin et al. (Houston). Four-state behavior, with two polarization states of the PZT gate, and both superconducting and normal states of the YBCO channel, has been observed. The authors found that the biased superconducting channel can be switched from the superconducting state to the normal state by applying a pulse on the PZT gate.
Theory
A preprint by S. E. Krasavin and N. M. Plakida (JINR-Dubna) proposes an effective two-band electron-phonon model for La2-xMxCuO4 (M = Sr, Ba, Ca) allowing for structural phase transitions among the hightemperature tetragonal (HTT), low-temperature orthorhombic (LTO), and low-temperature tetragonal (LTT) phases. Taking into account the electron-phonon interaction, the authors use the Green's function technique to derive a self-consistent system of equations for Tc. The authors calculate the dependence of Tc upon hole concentration in all three phases. A dip of Tc at the transition to the LTT phase is found to arise from the splitting of two oxygen bands at halffilling. This result is qualitatively consistent with experiments for Ba-doped materials.
According to H. L. Dewing and K. Scott (Cambridge), the temperature dependence observed in the mid- and near-infrared optical properties of YBa2Cu3O7-d can be explained in terms of the Drude model for free charge carriers. In the Drude model, the linear temperature dependence of the dc resistivity arises from the free charge carriers having a temperature-dependent mean free path. This temperature dependence results in the plasmon contribution to the dielectric constant having a damping coefficient that also varies linearly with temperature. The authors find that the temperature dependence that is observed in the absorption and reflection spectra of YBa2Cu3O7-d is consistent with this simple model.
Superconducting pairing via scattering of conduction electrons from interacting two-level tunneling states has been considered by S. B. Simanovsky and M. W. Klein (Worcester Polytechnic). In their model the phonon energy of the BCS theory is replaced by the interaction energy between the tunneling units. When this energy is sufficiently large, the transition temperature Tc may be quite high. Moreover, Tc is predicted to have no isotope effect.
A preprint by D. M. Eagles (NASA-Huntsville and Magnetic Power, Inc.) applies to quasi-one-dimensional systems the idea of R. H. Parmenter [Phys. Rev. 116, 1390 (1959); 140, A1952 (1965)] that pairing may be enhanced at high drift velocities in narrow cylindrical regions with thickness less than the magnetic-field penetration depth. The author discusses the applicability of these ideas to reports of roomtemperature superconductivity in narrow channels perpendicular to surfaces of films of oxidized polypropylene.
A theory by J. C. Phillips (AT&T Bell Labs) involving coherent resonant pinning, oxygen ordering, and high-temperature superconductivity is proposed to explain chemical trends in the families Bi2Sr2Can-1CunO4+2n+d, Tl2Ba2Can-1CunO4+2n+d, and HgBa2Can1CunO2+2n+d. The theory, which is based on conventional electronlattice interactions and utilizes no exotic concepts, directly relates Tc and its pressure derivative dTc/dP to structure.
Other Activities
A preprint by H. A. Blackstead (Notre Dame) and J. D. Dow (Arizona State) considers the fact that Nd^[3+] (J = 9/2) on a Ba site between a CuO2 plane and a CuO chain layer of superconducting NdBa2Cu3Ox (x ~~ 7) acts as a magnetic scatterer and pair-breaker, while Nd on a rare-earth site between two CuO2 planes does not. The authors argue that this implies that the superconductivity originates in the chain layers, not in the cuprate planes, of NdBa2Cu3Ox and its homologous compounds.
Measurements of the tunneling conductance spectra in Bi2Sr2CaCu2O8+d (Bi-2212) and La2-xSrxCuO4 (x = 0.2) single crystals are reported by R. Aoki et al. (Osaka). The authors report that above the gap structure, suggesting s-wave pairing, remarkable fine structures were reproducibly observed, ranging to the bias limit of 0.2 eV. The authors compare their conductance-derivative peaks with the phonondensity-of-states peaks reported by B. Renker et al. [Z. Phys. B 67, 15 (1987); 77, 65 (1989)] and find reasonable peak to peak correspondence. In Bi-2212, additional peaks in the tunneling conductance at energies above the Debye energy are identified as multi-phonon peaks, which have unexpectedly strong intensities.
A detailed study of neutron diffraction in La2NiO4+d single crystals as a function of oxygen excess delta (with 0.05 <= delta <= 0.11) and temperature T has been carried out by J. M. Tranquada (Brookhaven) et al. The results are summarized in a complex phase diagram in the delta-T plane. The authors report evidence for oxygen intercalation, ordering, and phase separation.
Model calculations have been carried out by D.-X. Chen and A. Hernando (IMA-Madrid) in an attempt to simulate the paramagnetic Meissner effect (PME). The authors considered the properties of 0-pi junctions, for which half of the junction width has its Josephson coupling energy per unit area minimized when the gauge-invariant phase difference across it is zero, and the other half has its Josephson coupling energy minimized for a phase difference of pi. The authors find that, while the model has some of the properties of the experimentally observed PME, it does not account for the observed field dependence of the magnetization.
A preprint by A. Chen (ICTP) et al. describes experiments on the properties of a ceramic composite of ferroelectric BaTiO3 and superconducting YBa2Cu3O7-d. The phases present were found to depend upon the composition regime. For low nominal YBa2Cu3O7-d content, the conductive characteristics of the two-phase BaTiO3 and YBa3Ti2O8.5 composition follow the three-dimensional percolation model, while for high nominal YBa2Cu3O7-d content, superconductivity was observed.
Overviews
An overview of various correlation effects in high-Tc superconductors and heavy-fermion compounds has been prepared by A. L. Kuzemsky (ICTP and JINR). The author discusses the role of charge and spin degrees of freedom, the Emery model, the t-J model, the Kondo-Heisenberg model, mixed valence states in oxides, charge transfer excitations, phase separation, and self-consistent nonperturbative techniques. A short review of the arguments supporting the spin-polaron mechanism in high-temperature superconductivity also is presented (161 references).
Recent progress on proximity-effect theory in superconductorferromagnet superlattices is reviewed by Z. Radovic and L. Dobrosavljevic-Grujic (Belgrade). The authors present calculations of phase diagrams, transition temperatures Tc, and upper critical fields H_[c2]. Characteristic features in the dependencies of Tc and H_[c2] upon layer thickness, including unusual oscillatory variations and a new inhomogeneous superconducting state with a phase difference of pi between adjacent superconducting layers, are discussed and compared with experimental data for V/Fe and Nb/Gd superlattices (36 references).
Contributed by John R. Clem ---------------------------------------------------------------------
Contents: Technology News begins on page 6; Preprints begin on page 7; Coming Events begin on page 14; Resources are on page 15; and FYI is on page 16.
---------------------------------------------------------------------
This section describes progress in manufacturing, product development, and technology transfer in the high-Tc superconductivity field. Please send your contributions (product development information, news regarding technology transfer efforts, or any information you would like to share about your corporation or laboratory) to the editor.
Scientists at Los Alamos National Laboratory have fabricated a hightemperature superconducting tape that has produced Jc ~~ 8 x 10^5 A/cm^2 at 77 K. The team developed a novel ion-assisted deposition method to sandwich cubic zirconia between the YBCO film and flexible Ni tape. Previous efforts to deposit YBCO on Ni have been unsuccessful because of random orientation of the grains and reaction of YBCO with Ni. In this work, the problem was overcome by using an intermediate buffer layer of cubic zirconia to add texture to the nickel surface, and using a second ion beam directed at the Ni tape at a specific angle to align the deposited zirconia grains. The alignment of the zirconia grains in turn force alignment of the YBCO, and gives rise to a new record for Jc for superconducting tapes deposited on a flexible metal substrate. For further information, contact Kathy Higgins, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 667-7000.
Researchers at Santa Clara University have made a silicon fieldeffect transistor using superconducting YBCO as the gate material and YSZ as the insulator. Two- and three-terminal devices were made by deposition of laser-ablated YBa2Cu3O7-d and YSZ on p-type Si (100) substrates. Standard lithography techniques were used. Gold contacts were evaporated on the YBCO gate and YSZ was selectively removed with ion milling. Capacitance vs. voltage (C-V) measurements reveal that the clockwise hysteresis between positively and negatively swept C-V curves reverses direction as the device cools. The researchers conclude that existence of a SiOx interfacial layer between the YSZ and Si gives rise to electrical characteristics that change from being dominated by mobile ions in YSZ to trapped charges in the interface. The scientists infer that existence of a SiOx interfacial layer between YSZ and Si is essential for maintaining the desired characteristics, and trapped charges at the SiOx/Si layer are primarily responsible for the superconductor-insulator-semiconductor device characteristics at superconducting temperatures. For further information, contact Jianmin Qiao, Microelectronics Laboratory, Santa Clara University, Santa Clara, CA 95053; telephone (408) 554-6817; telefax (408) 554-5474; e-mail jqiao@scuacc.scu.edu.
A liquid nitrogen level sensor, capable of measuring the level of liquid nitrogen in a cryogenic dewar with high accuracy, has been developed by Illinois Superconductor Corporation (ISC). The active element of this device is a high-temperature superconductor sensing filament. When a small electrical current is passed through the filament, the decreased heat transfer on the vapor side of the liquid-vapor interface causes the exposed superconducting wire to make a transition to its normal state in the vapor phase. Consequently, the voltage measured across the filament is proportional to the length of the filament exposed to the vapor. This phenomenon enables continuous measurement of cryogenic liquid levels even when the vapor filled head space above the liquid is at the same temperature as the liquid. The sensor has no moving parts, and requires simple electronics for operation. It is available in customer-specified active lengths of up to 30" and is sold as a stand-alone sensor that requires a 0-500 mA constant current source and voltmeter for operation. An integrated sensor and electronic unit is currently being developed. The sensor will operate in headspace temperatures down to 77 K and in ambient pressures ranging from 0-20 psi. The sensitivity is typically 0.22 V/in and a calibration curve is included with the sensor. For information, contact Illinois Superconductor Corporation, 1840 Oak Avenue, Evanston, IL 60201; telephone (708) 866-0435; telefax (708) 866-0439.
A lunar telescope using HTS bearings has been developed by researchers at the Texas Center for Superconductivity (TCSUH) at Houston, Texas, in collaboration with Computer Sciences Corporation (California) and NASA. A lunar telescope must have a bearing for its mount that can operate unmanned for long periods under extreme conditions. The patented bearing design by TCSUH does not need a coolant for the superconductor on the moon's surface if shielded from sunlight. Hybrid superconductor magnetic bearings (HSMB) are formed when superconductors are combined with permanent magnets. They are small in mass, stable, and rotate without friction. The superconductors trap and store the surrounding magnetic field leading to enhanced stability. Since there is no mechanical contact between the rotor and stator in these bearings, they do not wear out. A very small rotation rate of 0.1 micrometer/s is required to follow the stars across the entire night sky of the moon, and machinery that can provide this fine motion on earth is typically massive and impractical for space travel. The TCSUH telescope structure is about 40" tall, with a 22" base. The superconductors are housed in two structures, both 6.5" in diameter and 3" tall. The bearing assembly can support loads up to 10 lb., and its own weight is 15 lb. Although the bearings were developed for use on the moon, the TCSUH scientists believe they will eventually be used in earth-based applications as well as space and lunar applications. For further information, contact Susan Warren Butler, Associate Director for Public Affairs, Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8210; telefax (713) 743-8201.
Contributed by Sreeparna Mitra ---------------------------------------------------------------------
High-Tc Update is available without charge to interested persons. Recipients are expected to participate in this information exchange by sending us preprints, reprints, meeting news, research news, etc. Contributions to defray the cost of newsletter printing and mailing are welcome.
Bal K. Agrawal, Savitri Agrawal, and M. D. Tiwari, "Van Hove Singularity Scenario and Hole Concentration in High-Tc HgBa2CaCu2O6+d Superconductor: Pressure Effects." Department of Physics, Allahabad University, Allahabad 211 002, INDIA; telephone +91 532 608316.
P. Allenspach, J. Mesot, U. Staub, M. Guillaume, A. Furrer, S.-I. Yoo, M. J. Kramer, R. W. McCallum, H. Maletta, H. Blank, H. Mutka, R. Osborn, M. Arai, Z. Bowden, and A. D. Taylor, "Magnetic Properties of Nd^[3+] in Nd-Ba-Cu-O Compounds." To be published in Z. Phys. B. Laboratorium fuer Neutronenstreuung, ETH Zurich, CH-5232 Villigen PSI, SWITZERLAND; telephone +41 56 99 2527; telefax +41 56 99 2939; e-mail allenspach@cageir5a.bitnet. 71.70.Ch; 74.70.Vy.
Ryozo Aoki, Hironaru Murakami, and Toshiyuki Kita, "Tunneling Observation of Phonon Contribution to the Pairing Interaction in Oxide Superconductors." To be published in Physica C, Vol. 224 (in press). Department of Electrical Engineering, Osaka University, Suita, Osaka 565, JAPAN. Key words: tunneling, phonon mechanism, electron-phonon coupling energy gap, Eliashberg equation.
V. D. Ashkenazy, M. Bonaldi, G. Jung, I. B. Khalfin, B. Ya. Shapiro, and S. Vitale, "Random Telegraph Noise Spectra in Granular High-Tc Films." Submitted to Solid State Commun. Jack and Pearl Reznik Institute of Advanced Technology and Department of Physics, Bar-Ilan University, 52900 Ramat Gan, ISRAEL; G. Jung's telephone in BeerSheva, Israel +972 7 472124; telefax +927 7 281340; e-mail jung@chen.bgu.ac.il.
V. D. Ashkenazy, G. Jung, I. B. Khalfin, and B. Ya. Shapiro, "Random Signal Interaction with Flowing Lattice of Abrikosov Vortices." To be published in Physica C. Jack and Pearl Reznik Institute of Advanced Technology and Department of Physics, Bar-Ilan University, 52900 Ramat Gan, ISRAEL; G. Jung's telephone in Beer-Sheva, Israel +972 7 472124; telefax +927 7 281340; e-mail jung@chen.bgu.ac.il. 74.40.+k; 74.60.Ge; 74.76.Bz.
A.M.M. Barus and J.A.T. Taylor, "The Effect of Particle Size Distribution on the Phase Composition in YBa2Cu3O7-x as Determined by DTA." To be published in Physica C, Vol. 225 (in press). New York State College of Ceramics, Alfred University, Alfred, NY 14802. Key words: YBa2Cu3O7-x, DTA, crystallite size, atmosphere, peritectic.
G. Baskaran, "Failure of Fermi Liquid Theory in 2-D: A Signal from Perturbation Theory." Preprint #IMSc/94/17. The Institute of Mathematical Sciences, Madras 600 113, INDIA; e-mail baskaran@imsc.ernet.in.
D. Berling, D. Bolmont, D. Bourgault, P. Danesi, B. Loegel, A. Mehdaoui, and R. Tournier, "Influence de la Methode de Fabrication sur la Ligne d'Irreversibilite et l'Anisotropie des Supraconducteurs Haute Temperature Massifs." Presented at the Conf. on Supercond. with High-Critical Temp., Caen, France, Nov. 16-17, 1993. Laboratoire de Physique et de Spectroscopie Electronique (LPSE), URA 1435, Faculte des Sciences et Techniques, Universite de Haute Alsace, 4 rue des freres Lumiere, F-68093 Mulhouse Cedex, FRANCE; B. Loegel's telephone +33 89 59 63 40; telefax +33 89 59 63 59. In French.
D. Berling, D. Bolmont, D. Bourgault, P. Danesi, B. Loegel, A. Mehdaoui, and R. Tournier, "Influence of Processing on the Irreversibility Line and the Anisotropy of High Temperature Superconductors in the Low Field Limit." Presented at the 5th Int. Conf. on Modern Aspects of Supercond. (ICMAS-93), Paris, France, Dec. 13-15, 1993. Laboratoire de Physique et de Spectroscopie Electronique (LPSE), URA 1435, Faculte des Sciences et Techniques, Universite de Haute Alsace, 4 rue des freres Lumiere, F-68093 Mulhouse Cedex, FRANCE; B. Loegel's telephone +33 89 59 63 40; telefax +33 89 59 63 59. Key words: ac susceptibility, irreversibility line, flux pinning, anisotropy, fabrication technique.
S. M. Bhagat, "Low-Field Microwave Magnetoabsorption in the Cuprate Superconductors." Presented at the AMPERE Workshop on Magnetic Resonances and Microwave Absorption in the High-Tc Supercond. Mater., Poznan, Poland, April 10-13, 1994. Department of Physics and Center for Superconductivity Research, University of Maryland, College Park, MD 20742-4111.
S. Bhavaraju, J. F. DiCarlo, I. Yazdi, A. J. Jacobson, H. H. Feng, Z. G. Li, and P. H. Hor, "Electrochemical Intercalation of Oxygen in La2CuO4 at Ambient Temperature." Preprint #94:037; submitted to Mater. Res. Bull., March 30, 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201.
H. A. Blackstead, D. B. Pulling, J. S. Horwitz, and D. B. Chrisey, "Observation of Flux Flow in Superconducting YBa2Cu3O7-d Films." To be published in Phys. Rev. B. Department of Physics, University of Notre Dame, Notre Dame, IN 46556; telephone (219) 631-6386; telefax (219) 631-5952; e-mail blackstd@rems1.phys.nd.edu.
Howard A. Blackstead and John D. Dow, "Pair-Breaking by Ba-Site Magnetic Dopants in Superconducting NdBa2Cu3Ox." Department of Physics, University of Notre Dame, Notre Dame, IN 46556; telephone (219) 631-6386; telefax (219) 631-5952; e-mail blackstd@rems1.phys.nd.edu. 74.20.Fg; 74.70.Vy.
J. Boiko, P. Majewski, and F. Aldinger, "Flux Line Pinning by Defects in High-Tc Superconducting Crystals." Submitted to Cryst. Res. and Technol. Pulvermetallurgisches Laboratorium, Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 5, D-70569 Stuttgart, GERMANY. Key words: superconductor, defects, flux pinning, critical current density.
J. C. Booth, D. H. Wu, and Steven M. Anlage, "A Broadband Method for the Measurement of the Surface Impedance of Thin Films at Microwave Frequencies." To be published in Rev. Sci. Instrum., June 1994. Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742-4111; telephone (301) 405-7670; telefax (301) 314-9541; e-mail jb137@umail.umd.edu. 78.70.Gq; 74.60.Ge; 84.40.Rq; 73.61.At.
S. M. Bose, P. Longe, and Y. M. Malozovsky, "Plasmon Effects in a Layered Two-Dimensional Electron Gas." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Department of Physics and Atmospheric Science, Drexel University, Philadelphia, PA 19104.
Lev N. Bulaevskii and Marty P. Maley, "Quantum Fluctuations of Vortices in Josephson-Coupled Superconductors." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Los Alamos National Laboratory, Los Alamos, NM 87545.
R. Busch, G. Ries, G. Kreiselmeyer, M. Arnold, and G. SaemannIschenko, "Evidence for Interlayer Dissipative Processes in High-Tc Superconductors." Submitted to Phys. Rev. Lett., March 9, 1994. Physikalisches Institut, Universitaet Erlangen-Nuernberg, Erwin Rommel Strasse 1, D-91058 Erlangen, GERMANY. 74.50.+r; 74.60.Ge.
V. Caignaert, I. Mirebeau, F. Bouree, N. Nguyen, A. Ducouret, J.-M. Greneche, and B. Raveau, "Crystal and Magnetic Structure of YBaCuFeO5." To be published in J. Solid State Chem. Laboratoire CRISMAT-ISMRA, Boulevard du Marechal Juin, F-14050 Caen Cedex, FRANCE.
S. A. Carter, B. Batlogg, R. J. Cava, J. J. Krajewski, W. F. Peck, Jr., and H. Takagi, "Electron Density of States in the Boro-Carbide Intermetallic Superconductors." Submitted to Phys. Rev. B, April 1994. AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974; B. Batlogg's telephone (908) 582-6663; telefax (908) 582-3260.
CAO Xiaowen, "Thermally Activated Hopping in Dy1-xPrxBa2Cu3O7-y System." To be published in Acta Physica Sinica. Institute of Plasma Physics, Academia Sinica, Hefei 230031, PEOPLE'S REPUBLIC OF CHINA. 71.50.+t; 72.20.Fr; 72.80.
G. Celotti, A. Tampieri, R. Masini, and M. C. Malpezzi, "Evaluation of Structure-Related Parameters of Hot-Pressed BISCCO (2223) Phase." To be published in Physica C, Vol. 225 (in press). IRTEC-CNR, Research Institute for Ceramic Technology, via Granarolo 64, I-48018 Faenza, ITALY.
R. Chatterjee, S. Aoki, M. Fukutomi, K. Komori, K. Togano, and H. Maeda, "Transport Properties and Surface Morphology in Y123 Films on Metallic Substrates with Grain-Oriented Buffer Layer." To be published in Physica C, Vol. 224 (in press). National Research Institute for Metals, Tsukuba Laboratories, 1-2-1 Sengen, Tsukubashi, Ibaraki 305, JAPAN. Key words: thin films on metallic substrates, surface morphology, grain orientation, texturing.
Ang Chen, Yu Zhi, Yahua Bao, and Xi Dai, "A Study of Ceramic Composite of Ferroelectric BaTiO3 Ceramic and Superconductor YBa2Cu3O6+d Ceramic." Preprint #IC/93/385. International Centre for Theoretical Physics, P.O. Box 586, I-34100 Trieste, ITALY; telephone +39 40 224241; telefax +39 40 224531; telex 460449 APHI; cable CENTRATOM TRIESTE.
D.-X. Chen and A. Hernando, "Paramagnetic Meissner Effect and 0-pi Josephson Junctions." To be published in Europhys. Lett. Laboratorio "Salvador Velayos", Instituto de Magnetismo Aplicado, RENFE-UCM, P.O. Box 155, 28230 Las Rozas, Madrid, SPAIN; telephone +34 1 630-1724 or -4278; telefax +34 1 630-1625; e-mail duxing@ima.ucm.es. 72.25.Ha; 74.25.Bt; 74.72.-h.
J. W. Chen, "Upper Critical Magnetic Fields of Bi2Sr2CuO6 Single Crystals." To be published in Physica C, Vol. 225 (in press). Department of Physics, National Taiwan University, Taipei, Taiwan, REPUBLIC OF CHINA.
A.J.S. Chowdhury, B.M.R. Wanklyn, F. R. Wondre, J. W. Hodby, A. V. Volkozub, and P.A.J. de Groot, "Growth of High-Quality 2212 BSCCO Crystals in Pt Crucibles and Characterization." To be published in Physica C, Vol. 225 (in press). National Crystal Growth Facility for Superconducting Oxide Crystals, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UNITED KINGDOM. Key words: BSCCO 2212 crystals, Pt crucible, novel flux method, purity, highest Tc 2212 phase.
K. Conder, Ch. Krueger, E. Kaldis, D. Zech, and H. Keller, "Is the Splitting of the Superconducting Transition in YBa2Cu3O7-x (x < 0.05) Due to Oxygen-Diffusion Limitations?" To be published in Physica C, Vol. 225 (in press). Laboratorium fuer Festkoerperphysik, ETHHoenggerberg, CH-8093 Zurich, SWITZERLAND.
D. W. Cooke, J. L. Smith, S.F.J. Cox, A. Morrobel-Sosa, R. L. Lichti, T. L. Estle, B. Hitti, L. C. Gupta, R. Nagarajan, Z. Hossain, C. Mazumdar, and C. Godart, "Muon Spin Relaxation Measurements of Coexistent Magnetism and Superconductivity in RENi2B2C (RE = Tm,Lu)." Preprint #LA-UR-94-1286; submitted to Phys. Rev. Lett., April 1994. Mail Stop H846, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 667-4274; telefax (505) 665-7920. 74.25.Ha; 74.70.Ad; 76.75.+i.
H. L. Dewing and K. Scott, "Temperature Dependence of the Infrared Optical Properties of YBa2Cu3O7: A Plasmon Damping Model." To be published in J. Supercond., Vol. 7 (in press). Contact H. L. Dewing, c/o B. Guettler, Physikalisch-Technische Bundesanstalt, Lab. 3.31, Bundesallee 100, D-38116 Braunschweig, GERMANY; telephone +49 531 592 3316; telefax +49 531 592 3015. Key words: high-Tc superconductors, YBa2Cu3O7, infrared, plasmon, resistivity.
D. M. Eagles, "Possible High-Current Superconductivity at Room Temperature in Oxidized Polypropylene and Other Quasi One-Dimensional Systems." To be published in Physica C. Centre de Recherches sur la Physique des Hautes Temperatures, CNRS, F-45071 Orleans Cedex 2, FRANCE. Key words: room-temperature superconductivity, high-current superconductivity, oxidized polypropylene.
N. Q. Fan, "Macroscopic Quantum Spectroscopy of Josephson Junctions." Preprint #94:039; submitted to Phys. Rev. Lett., March 30, 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201. 74.50.+r; 03.65.Bz; 85.25.Cp; 85.25.Dq.
E. Faulques, P. Mahot, M. Spiesser, T. P. Nguyen, G. Garz, C. Gonzalez, and P. Molinie, "Oxygen Sublattice Ordering and Intercalation Mechanism of Chlorine in YBa2Cu3O6+d." To be published in Phys. Rev. B (in press). Laboratoire de Physique Cristalline, Institut des Materiaux de Nantes, UMR 110, CNRS-Universite de Nantes, 2 rue de la Houssiniere, F-44072 Nantes Cedex 03, FRANCE; telephone +33 40 37 39 98; telefax +33 40 37 39 91. Key words: oxygen sublattice, chlorine insertion, Raman spectra, magnetization. 74.70.Vy; 78.30; 75.20.
Mark Friesen, "Vortex Unbinding and Layer Decoupling in a Quasi-2D Superconductor." Submitted to Phys. Rev. Lett. School of Physics and Astronomy, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455-0149; telephone (612) 624-2327; telefax (612) 624-4578; e-mail friesen@physics.spa.umn.edu. 74.40.+k; 74.50.+r; 74.80.Dm; 74.72.-h.
K. Ghosh, Kristian Jonason, S. Ramakrishnan, and Girish Chandra, "Superconductivity in Quaternary LuCo2B2C." Submitted to the IVth Int. Conf. on Mater. and Mechanisms of Supercond. and High-Temp. Supercond. (M^2S-HTSC-IV), Grenoble, France, July 4-9, 1994. Contact S. Ramakrishnan, Low Temperature Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Bombay 400 005, INDIA; telephone +91 22 215-2971 or -2979; telefax +91 22 215-2110; e-mail ramky@tifrvax.bitnet. 74.70.Ad; 74.25.Bt; 74.25.Ha.
K. Ghosh, S. Ramakrishnan, Kristian Jonason, and Girish Chandra, "Superconductivity in Quaternary YCo2B2C." Submitted to Phys. Rev. Lett., March 15, 1994. Contact S. Ramakrishnan, Low Temperature Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Bombay 400 005, INDIA; telephone +91 22 215-2971 or -2979; telefax +91 22 215-2110; e-mail ramky@tifrvax.bitnet. 74.70.Ad; 74.25.Bt; 74.25.Ha.
V. M. Gvozdikov, "Electromagnetic Waves in Layered Superconductors." To be published in Physica C, Vol. 224 (in press). Department of Physics, Kharkov State University, 310077 Kharkov, UKRAINE. Key words: electromagnetic waves, layered superconductors and superlattices.
T. J. Hagenaars, P.H.E. Tiesinga, J. E. van Himbergen, and Jorge V. Jose, "Nonlinear Viscous Vortex Motion in Two-Dimensional Josephson Junction Arrays." Institut voor Theoretische Fysica, Princetonplein 5, Postbus 80006, 3508 TA Utrecht, THE NETHERLANDS; e-mail hagenaar@fys.ruu.nl. 74.50.+r; 74.60.Ge; 74.60.Jg; 74.70.Mq.
Zhidong Hao and Chia-Ren Hu, "Flux Motion in Anisotropic Type-II Superconductors Near H_[c2]: II. Arbitrary Vortex Orientation." Submitted to Phys. Rev. B, April 7, 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201. 74.20.De; 74.25.Fy.
N. M. Hong, H. Michor, M. Vybornov, T. Holubar, P. Hundegger, W. Perthold, G. Hilscher, and P. Rogl, "Superconductivity in Y-Ni-B Base Compounds." Submitted to Physica C, March 9, 1994. Institut fuer Experimentalphysik, Technische Universitaet Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, AUSTRIA; G. Hilscher's telephone +43 1-58801/5770; telefax +43 1-564203 or -5863191; T. Holubar's e-mail tholubar@email.tuwien.ac.at. Key words: x-ray diffraction, specific heat, magnetic measurement.
A. N. Iyer, U. Balachandran, L. R. Motowidlo, J. G. Hoehn, Jr., and P. Haldar, "Fabrication and Characteristics of Tapes and Test Magnets Made from Ag-Clad Bi-2223 Superconductors." Submitted to J. Electronic Mater., Feb. 1994. Energy Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439.
V. Jeudy, G. Jung, D. Limagne, and G. Waysand, "Irreversible Flux Penetration Regimes in Type-I Superconducting Strips." To be published in Physica C, Vol. 225 (in press). Groupe de Physique des Solides, CNRS-URA 17, Universites Paris VII et Paris VI, Universite Paris VII-Tour 23, F-75251 Paris Cedex 05, FRANCE. 74.55+h.
M. Kall, A. P. Litvinchuk, P. Berastegui, L.-G. Johansson, and L. Boerjesson, "Temperature Dependence of Phonon Raman Scattering in Y2Ba4Cu7O15-d." To be published in Physica C, Vol. 225 (in press). Department of Physics, Chalmers University of Technology, S-412 96 Goeteborg, SWEDEN. Key words: phonon spectrum, Raman scattering, energy gap.
Chan-Joong Kim, Dong-Yeon Won, Hong-Chul Moon, and Dong-Soo Suhr, "Formation of BaCeO3 and Its Influence on Particle Size of Y2Ba1Cu1O5 of Melt-Textured Y-Ba-Cu-O Oxides with CeO2 and Y2Ba1Cu1O5." To be published in J. Mater. Res. Superconductivity Research Department, Korea Atomic Energy Research Institute, P.O. Box 7, Daeduk-danji, Daejon 305-353, KOREA; telephone +82 42 820 2317; telefax +82 42 862 5496.
O. Klein, E. J. Nicol, K. Holczer, and G. Gruener, "Conductivity Coherence Factors in Conventional Superconductors Nb and Pb." Submitted to Phys. Rev. B, March 28, 1994. Room 13-2106, Center for Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307; telephone (617) 253-1580; telefax (617) 258-6478; e-mail olivier@kastner.mit.edu.
*Richard A. Klemm and Samuel H. Liu, "Intra- Versus Interlayer Pairing in the Copper Oxide Superconductors: Response to a Magnetic Field." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439. *Revised manuscript.
L. Z. Kon and I. P. Ciobanu, "Collective Oscillations in Superconductors with Electron-Hole Asymmetry." To be published in Physica C, Vol. 224 (in press). Institute of Applied Physics, Academy of Sciences of Moldova, Academiei Str. 5, 277028 Kishinev, MOLDOVA. Key words: BCS model, Anderson model, fluctuation effects.
R.T.W. Koperdraad and A. Lodder, "Application of Proximity Effect Theory to Metallic Multilayers." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 2228, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Faculty of Physics and Astronomy, Free University, De Boelelaan 1081, 1081 HV Amsterdam, THE NETHERLANDS.
T. Koyama and M. Tachiki, "Fluctuations in Layered Superconductors." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980, JAPAN.
S. E. Krasavin and N. M. Plakida, "Superconductivity in Tetragonal and Orthorhombic Structural Phases of La2-xMxCuO4." Bogolubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980, RUSSIA.
V. V. Kurin and A. I. Panfilov, "Flux Lines and Lattices in Superconductors with Additional Ordering." To be published in Physica C, Vol. 224 (in press). Institute of Applied Physics, Russian Academy of Sciences, 46 Uljanov Str., Nizhny Novgorod 603600, RUSSIA.
E. Z. Kurmaev, V. V. Fedorenko, L. V. Elokhina, L. D. Finkelstein, and T. B. Popova, "X-ray Emission Spectra and Analysis of F-Doping of Bi2212 Compound." To be published in Physica C, Vol. 225 (in press). Institute of Metal Physics, Russian Academy of Sciences-Ural Division, 620219 Yekaterinburg GSP-170, RUSSIA.
A. L. Kuzemsky, "Correlation Effects in High-Tc Superconductors and Heavy Fermion Compounds." Preprint #IC/93/336; presented at the Int. Conf. on Supercond. and Strongly Correlated Electron Systems, Amalfi, Italy, Oct. 14-16, 1993. International Centre for Theoretical Physics, P.O. Box 586, I-34100 Trieste, ITALY; telephone +39 40 224241; telefax +39 40 224531; e-mail kuzemsky@theor.jinrc.dubna.su.
Saswati Lahiry, Y. S. Reddy, B. Sarkar, R. Rajput, D. K. Suri, R. G. Sharma, and B. B. Sharma, "Mercury-Enhanced High Tc in the Bi(Pb)-SrCa-Cu-O System." To be published in Physica C, Vol. 225 (in press). Contact R. G. Sharma, Department of Physics, University of Delhi, Delhi 110 007, INDIA. Key words: electrical resistivity, transition temperature, ac susceptibility, charge transfer, oxidation state.
D. F. Lee, C. S. Partsinevelos, R. G. Presswood, Jr., and K. Salama, "Melt-Texturing of Preferentially Aligned YBa2Cu3Ox Superconductor by a Seeded Directional Solidification Method." Preprint #94:036; to be published in J. Appl. Phys., July 1, 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201.
A. I. Liechtenstein, I. I. Mazin, O. K. Andersen, and O. Jepsen, "Theoretical Search for a Bistability of Apical Oxygen in YBa2Cu3O7." Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; e-mail liechten@radix6.mpistuttgart.mpg.de.
C. T. Lin and W. Y. Liang, "Etch Defects in YBa2Cu3O7-d Single Crystals Grown from Flux." To be published in Physica C, Vol. 225 (in press). Interdisciplinary Research Centre in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UNITED KINGDOM.
H. Lin, N. J. Wu, K. Xie, X. Y. Li, and A. Ignatiev, "The Transient Behavior and Memory Effect of a PZT/YBCO Three-Terminal Device." Preprint #94:042; submitted to Appl. Phys. Lett., April 4, 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201.
M. Lorenz, H. Hochmuth, H. Boerner, D. Natusch, and K. Kreher, "Large Area Pulsed Laser Deposition of YBCO Thin Films and Buffer Layers on 3-Inch Wafers." To be published in the Proc. of the MRS Spring Mtg.: Symp. F on Epitaxial Oxide Thin Films and Heterostructures, San Francisco, CA, April 4-8, 1994. Institut fuer Experimentalphysik II, Universitaet Leipzig, Linnestrasse 5, D-04103 Leipzig, GERMANY.
J. W. Lynn, N. Rosov, T. E. Grigereit, H. Zhang, and T. W. Clinton, "Vortex Dynamics and Melting in Niobium." Submitted to Phys. Rev. Lett. Reactor Radiation Division, National Institute of Standards and Technology, Gaithersburg, MD 20899. 74.60.Ge; 74.25.Dw; 74.70.Ad; 61.12.-q.
S. Mahajan, J. G. Wen, W. Ito, C. H. Cho, T. Takenaka, N. Kubota, Y. Yoshida, and T. Morishita, "Comparison of Crystalline and Superconducting Properties of Sputtered a-Axis Oriented YBCO Films on MgO and SrTiO3 Substrates." To be published in Physica C, Vol. 225 (in press). Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone +81 3 3536-5703 through -5705; telefax +81 3 3536-5714 or -5717.
Peter Majewski, Huang-Lung Su, and Fritz Aldinger, "The Oxygen Content of the High-Temperature Superconducting Compound Bi2+xSr3yCayCu2O8+d as a Function of the Cation Concentration." Submitted to Physica C. Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 5, D-70569 Stuttgart, GERMANY.
A. W. McConnell, R. A. Hughes, A. Dabkowski, H. A. Dabkowska, J. S. Preston, J. E. Greedan, and T. Timusk, "Evaluation of LaSrGaO4 as a Substrate for YBa2Cu3O7-d." To be published in Physica C, Vol. 224 (in press). Contact R. A. Hughes, Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, CANADA. Key words: substrates, thin films, applications of high-Tc superconductors, electrical resistivity, critical current density, scanning electron microscopy.
Frederic Mila, "Exact Result on the Mott Transition in a TwoDimensional Model of Strongly Correlated Electrons." Laboratoire de Physique Quantique, Universite Paul Sabatier, F-31062 Toulouse Cedex, FRANCE. 71.10.+x; 75.10.-b; 71.30.+h; 72.15.Nj.
J. Mosqueira, A. Pomar, A. Diaz, J. A. Veira, and Felix Vidal, "Resistivity Anomalies Above the Superconducting Transition in Y1Ba2Cu3O7-d Crystals and Non-Uniformly Distributed CriticalTemperature Inhomogeneities." To be published in Physica C, Vol. 224 (in press). Contact Felix Vidal, LAFIMAS, Facultad de Fisica, Universidad de Santiago, 15706 Santiago de Compostela, SPAIN. 74.25.Fy; 74.62.-c; 74.72.-h.
R. Movshovich, M. F. Hundley, J. D. Thompson, P. C. Canfield, B. K. Cho, and A. V. Chubukov, "Specific Heat of Single Crystal YNi2B2C and TmNi2B2C Superconductors." Preprint LA-UR-94-940; submitted to Physica C. Los Alamos National Laboratory, Los Alamos, NM 87545. Key words: YNi2B2C, TmNi2B2C, specific heat, antiferromagnetic order, crystal field, energy gap.
M. Nilsson-Mellbin and K. Salama, "Effect of Applied Magnetic Field on the I-V Characteristics of Melt-Textured YBa2Cu3O7-x Superconductors Containing Grain Boundaries." Preprint #94:035; to be published in Physica C. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 7438200; telefax (713) 743-8201. Key words: I-V characteristics, grain boundaries, YBa2Cu3O7-x.
M. Grant Norton, Rand R. Biggers, I. Maartense, E. K. Moser, and Jeff L. Brown, "Examination of Particles and Outgrowths on the Surface of Epitaxial YBa2Cu3O7 Thin Films." To be published in Epitaxial Oxide Thin Films and Heterostructures: MRS Symp. Proc. Series, Vol. 341, 1994, edited by D. K. Fork et al. Department of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920; telephone (509) 335-8654; telefax (509) 335-4662.
A. S. Parikh, B. Meyer, and K. Salama, "A Method to Improve Grain Boundary Current Carrying Capability in Melt Textured YBa2Cu3O7-d." Preprint #94:040; to be published in Supercond. Sci. & Technol., June 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 7438201. 74.70.
J. C. Phillips, "Coherent Resonant Pinning, Oxygen Ordering, and High-Temperature Superconductivity in the Multilayer Cuprates." AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974.
Stephen W. Pierson, "Critical Behavior of Vortices in a Layered System." Code 6877, Naval Research Laboratory, Washington, DC 203755347; e-mail pierson@estd.nrl.navy.mil. 74.72.-h; 64.60.Cn; 74.25.q; 74.80.Dm.
S. V. Pokrovsky and V. L. Pokrovsky, "Plasma Resonance in Layered Normal Metals and Superconductors." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Contact V. L. Pokrovsky, Department of Physics, Texas A & M University, College Station, TX 77843-4242.
A. Pomar, M. V. Ramallo, J. Maza, and Felix Vidal, "Measurements of the Fluctuation-Induced Magnetoconductivity in the a-Direction of an Untwinned Y1Ba2Cu3O7-d Single Crystal in the Weak Magnetic Field Limit." To be published in Physica C, Vol. 225 (in press). Contact Felix Vidal, LAFIMAS, Departamento de Fisica de la Materia Condensada, Facultad de Fisica, Universidad de Santiago, Santiago de Compostela 15706, SPAIN. Key words: critical phenomena, electrical resistivity, fluctuation effects.
A. K. Pradhan, P. Chaddah, S. B. Roy, and Chen Changkang, "Study of Magnetization in Pb2Sr2Y1-xCaxCu3O8+y Crystal: Fish-Tail Anomaly." To be published in Supercond. Sci. & Technol. (in press). Low Temperature Physics Group, Centre for Advanced Technology, Indore 452 013, INDIA. Key words: fish tail, magnetization hysteresis, time decay, oxygen defects, PSYCCO crystal. 74.30.Ci; 74.60.Ge.
A. K. Pradhan, S. B. Roy, P. Chaddah, C. Chen, and B. M. Wanklyn, "Magnetic Properties of Single Crystal Bi2Sr2CaCu2O8+y: Experimental Evidence for a Dimensional Crossover." To be published in Phys. Rev. B (in press). Low Temperature Physics Group, Centre for Advanced Technology, Indore 452 013, INDIA. 74.30.Ci; 74.60.Ge; 74.60.Jg.
Zoran Radovic and Lj. Dobrosavljevic-Grujic, "Phase Diagram of Superconductor-Ferromagnet Superlattices." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Department of Physics, University of Belgrade, P.O. Box 550, 11001 Belgrade, YUGOSLAVIA.
P. Rodrigues, Jr., J. Schaf, and P. Pureur, "Field and Oxygen Dependence of the Magnetic Irreversibility Line in YBa2Cu3O7-d." To be published in Phys. Rev. B, Vol. 49 (in press). Instituto de Fisica, Universidade Federal do Rio Grande do Sul, P.O. Box 15051, 91501-970 Porto Alegre, Rio Grande do Sul, BRAZIL. 74.72.Bk; 74.80.Bj; 74.25.Ha.
E. Rosseel, M. Baert, K. Temst, C. Potter, V. V. Moshchalkov, Y. Bruynseraede, P. Lobotka, I. Vavra, R. Senderak, and M. Jergel, "Critical Fields of W/Si Multilayers." To be published in Physica C, Vol. 225 (in press). Laboratorium voor Vaste-Stof Fysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B3001 Leuven, BELGIUM. Key words: superconductivity, multilayer, critical field, dimensional crossover.
I. Rusakova, A. Hamed, and P. H. Hor, "Effects of Deposition Temperature and Thermal Treatment on the Structure of C60 and C70 Films." Preprint #94:041; submitted to the Proc. of the MRS Spring Mtg., San Francisco, CA, April 4-8, 1994. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201.
Seungoh Ryu, S. Doniach, and A. Kapitulnik, "The Nature of Long Range Order in the Vortex Lattice of High Tc Superconductors." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Department of Applied Physics, Stanford University, Stanford, CA 94305.
Alvaro Sanchez, "Comparison Between Transport and MagneticallyInduced Critical-Current Density in High-Tc Superconductors." To be published in Physica C. Grup d'Electromagnetisme, Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, SPAIN; telephone +34 3 581 13 50; telefax +34 3 581 21 55; telex 52040 EDUCI E. 74.60.Jg; 74.72.-h; 74.60.-w.
Susumu Sasaki, Azusa Matsuda, and C. W. Chu, "Fermi-Liquid Behavior and BCS s-Wave Pairing of K3C60 Observed by [13]^C-NMR." To be published in J. Phys. Soc. Jpn., Vol. 63. NTT Basic Research Laboratories, Matsuda Group, 4S-322S, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-01, JAPAN; telephone +81 462 40 3537; telefax +81 462 40 4724; e-mail sasaki@will.ntt.jp. Key words: K3C60, [13]^C-NMR, constant-T1T, Fermi liquid, Hebel-Slichter peak, BCS s-wave, Eliashberg theory, strong electron correlation.
P.V.P.S.S. Sastry and A. R. West, "Stoichiometry and Tc of Bi-2201 Doped with La, Pr, Nd and Pb." To be published in Physica C. Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB9 2UE, Scotland, UNITED KINGDOM; telephone +44 224 272916, -944 or -943; telefax +44 224 272-921; e-mail sastry@aberdeen.ac.uk.
P.V.P.S.S. Sastry, J. V. Yakhmi, and R. M. Iyer, "On the Instability of Y- and Rare Earth-Substituted Bi(Pb)-2223 Phase." To be published in J. Mater. Chem. (in press). Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB9 2UE, Scotland, UNITED KINGDOM; telephone +44 224 272-916, -944 or -943; telefax +44 224 272-921; email sastry@aberdeen.ac.uk.
G. V. Sayko, A. S. Bugaev, and A. F. Popkov, "Interaction of Magnetoacoustic Waves with Flux-Line Lattice in SuperconductingFerrite Layered Structure." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 2228, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Theoretical Department, General Physics Institute, Vavilov St. 38, Moscow 117942, RUSSIA.
T. Schneider, "Pairing Fluctuations in Cuprate Superconductors: Universal Properties and Trends." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). IBM Research Division, Zurich Research Laboratory, Saeumerstrasse 4, CH-8803 Rueschlikon, SWITZERLAND.
A. C. Sharma and Ina Kulshrestha, "Collective Excitations Below Tc in Cuprate Superconductors." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 2228, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). School of Studies in Physics, Jiwaji University, Gwalior 474 011, INDIA.
Sergey B. Simanovsky and Michael W. Klein, "Superconducting Pairing via Excitations from Tunneling Units." Department of Physics, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280; telephone (508) 831-5258; telefax (508) 831-5886.
E. B. Sonin and K. B. Traito, "The Surface Impedance of a Type-II Superconductor in dc Magnetic Fields Parallel and Tilted to the Superconductor Border." A. F. Ioffe Physico-Technical Institute, St. Petersburg 194021, RUSSIA. 74.30.Gn; 74.30.Ci.
E. D. Specht, A. Goyal, D. M. Kroeger, J. A. DeLuca, J. E. Tkaczyk, C. L. Briant, and J. A. Sutliff, "X-ray Microdiffraction Analysis of mm-Scale Orientational Correlations in Tl-1223 High-Critical-Current, High-Temperature Superconducting Films." To be published in Physica C, Vol. 225 (in press). Building 4500S, MS 6118, Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6118; telephone (615) 574-7682; telefax (615) 574-7659; e-mail esy@ornl.gov. Key words: critical current density, grain alignment, x-ray diffraction.
Masashi Tachiki, Saburo Takahashi, and Tomio Koyama, "Low Frequency Plasma in Cuprate Superconductors and Related Phenomena." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980, JAPAN.
S. Takahashi, T. Hirai, and M. Tachiki, "Mechanism for the Peak Effect of the Critical Current in Superconducting Multilayers." To be published in the Proc. of the SPIE Int. Symp. on Optoelectronics and Microwave Engineering (OE/LASE '94): Supercond. Lattices and Multilayers, Los Angeles, CA, Jan. 22-28, 1994, No. 2157, edited by Ivan Bozovic (SPIE, Bellingham, in press). Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980, JAPAN.
Tineke Thio and Amnon Aharony, "Weak-Ferromagnetism and Tricriticality in Pure La2CuO4." NEC Research Institute, Princeton, NJ 08540. 75.30.Kz; 74.72.Dn; 74.40.Cx; 75.50.Ee.
J. M. Tranquada, Y. Kong, J. E. Lorenzo, D. J. Buttrey, D. E. Rice, and V. Sachan, "Oxygen Intercalation, Ordering, and Phase Separation in La2NiO4+d with 0.05 <= delta<= 0.11." Submitted to Phys. Rev. B. Department of Physics, Brookhaven National Laboratory, Upton, NY 11973. 61.72.Dd; 61.50.Ks; 61.12.-q; 75.50.Ee.
*C. C. Tsuei, J. R. Kirtley, C. C. Chi, Lock See Yu-Jahnes, A. Gupta, T. Shaw, J. Z. Sun, and M. B. Ketchen, "Pairing Symmetry and Flux Quantization in a Tri-Crystal Superconducting Ring of YBa2Cu3O7-d." Contact J. R. Kirtley, IBM Thomas J. Watson Research Center, Room 39028, P.O. Box 218, Yorktown Heights, NY 10598-0218; telephone (914) 945-2043; telefax (914) 945-3785; e-mail kirtley@ibm.watson.com. *Relisted.
ZHANG Li-Yuan, ZHOU Yun-Song, and JIN Guang-Hai, "On the Superconducting Mechanism of K3C60 and Ba1-xKxBiO3." To be published in Acta Physica Sinica in English. Department of Physics, Peking University, Beijing 100871, PEOPLE'S REPUBLIC OF CHINA; telephone +86 1 2561166, ext. 3468. 74.00; 74.20.
P. Zoller, J. Glaser, A. Ehmann, C. Schulz, W. Wischert, S. KemmlerSack, T. Nissel, and R. P. Huebener, "Superconductivity and Processing of Single Bi-O Layered Cuprates in the (Bi,Pb)-Sr-(Ca,Y)Cu-O System." Submitted to Physica C. Institut fuer Anorganische Chemie, Universitaet der Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen, GERMANY.
---------------------------------------------------------------------
*June 20 - 23, 1994: The 6th Joint MMM-Intermag Conference, Albuquerque Convention Center, Albuquerque, NM. The technical subject categories are: cooperative phenomena and fundamental magnetic properties, transport properties and elastic effects, magnetic excitations and high-frequency phenomena, soft magnetic materials and applications, hard magnetic materials and applications, other materials, specific geometries, computational magnets, magnetic recording, and interdisciplinary topics. Invited talks, oral presentations, and poster sessions. Special sessions on superconductivity. Exhibition of services, equipment, and materials. For information, contact Diane Suiters, MMM Conference Coordinator, Suite 300, 655 15th Street, NW, Washington, DC 20005; telephone (202) 639-5088; telefax (202) 347-6109.
*June 28 - 30, 1994: 8th International Cryocooler Conference, Westin Resort Hotel, Vail, CO. Invited technical topics include: Stirling, pulse-tube, J-T, Sorption, G-M and TEC cryocoolers; new cryocooler concepts; cryocooler component developments; modeling and test techniques; performance test data; cryocooler integration techniques; and application and life-test data. Oral and poster sessions. Opportunity for informal technical interaction. Preregistration deadline, May 27, 1994. Pre-registration fee, $275. Contact Dr. Ron Ross, 8th ICC Chairperson, M/S 233-105, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109; telephone (818) 354-9349; telefax (818) 393-4206 or Pat McLane, M/S T-1166, at the above address; telephone (818) 354-5556; telefax (818) 393-4992.
*July 4 - 9, 1994: 4th International Conference on Materials and Mechanisms of Superconductivity and High-Temperature Superconductors (M2S-HTSC-IV), Grenoble, France. Continuing tradition begun in Interlaken (1988), Stanford (1989), and Kanazawa (1991). Main topics: (1) superconducting materials: synthesis; crystal growth; thin films and multilayers; oxide, C60, and organic superconductors; crystallographic characterization; anion and cation substitutions; point and extended defects; (2) physical properties of superconductors: transport, magnetic, thermal, and optical properties; heavy electrons; vortices; vibration and lattice properties; neutron scattering; NM and NQ resonances; spectroscopies; critical current and flux pinning; (3) mechanisms and theory: electronic structure; properties of the normal and superconducting phases; electron correlations and localization; lattice and magnetic properties; (4) applications: tunneling effects; Josephson electronics; microwave properties; SQUIDs; detectors; magnetic bearings; superconducting magnets; ac and dc cold machines; current transmission; and other devices. Conference language, English. Chairpersons: Michel Cyrot and Pierre Monceau. Contact M2S-HTSC-IV Secretariat, CNRS, 25 av. des Martyrs, 38000 Grenoble Cedex 9, France, or M2S-HTSC-IV Secretariat, CNRS, BP 166, 38042 Grenoble Cedex 9, France; telephone +33 76 88 12 30; telefax +33 76 88 12 95.
*Sept. 7 - 9, 1994: 7th Conference on Superconductivity and Applications, Buffalo, NY. Sponsored by the New York State Institute on Superconductivity. Topics include: anisotropy and flux motion, bulk processing and the grain-boundary problem, energy storage, highfield nuclear magnetic resonance, maglev in New York State, molecular and organic superconductors, power applications, superconducting motors and generators, and physics and applications of tunneling. Conference chair: Michael J. Naughton. Abstract deadline, May 15, 1994. Contact Barbara Routhier, Conference Secretary, New York State Institute on Superconductivity, 330 Bonner Hall, State University of New York at Buffalo, Buffalo, NY 14620; telephone (716) 645-3114; telefax (716) 645-3349.
Feb. 12 - 16, 1995: Synthesis, Processing and Large Scale Applications of High-Temperature Superconductors, 1995 TMS Annual Meeting, Las Vegas, NV. Purpose is to bring together those actively engaged in research on synthesis, fabrication, and applications of oxide superconductors to discuss future prospects and directions for R&D. Topics include, but are not limited to, powder synthesis and novel processing; chemistry, phase relationships, and nonstoichiometry; relationships between microstructure and properties; flux pinning; processing for the development of flux-pinning centers; fabrication of wires, tapes, magnets, and bulk materials; and applications and future trends in high-temperature superconductors. Proceedings to be published in a special issue of the J. Electron. Mater. Abstract deadline, June 30, 1994. Send abstracts to Dr. U. (Balu) Balachandran, Ceramics Section, Energy Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439-4838, telephone (708) 252-4250, telefax (708) 252-3604, e-mail u_balachandran@qmgate.anl.gov; or Prof. Paul J. McGinn, Center for Materials Science and Engineering, Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, telephone (219) 631-6151, telefax (219) 631-4393, e-mail mcginn.1@nd.edu; or Dr. Donald U. Gubser, Materials Science and Technology Division, Code 6300, Naval Research Laboratory, Washington, DC 20375-5343, telephone (202) 767-2926, telefax (202) 404-8009, e-mail gubser@anvil.nrl.navy.mil. ---------------------------------------------------------------------
DOE Program Summary Book: Materials Sciences Programs-Fiscal Year 1993. Contents of this multiple-indexed book include descriptions for 472 research programs including 219 programs at 14 DOE National Laboratories, 242 research grants (237 at universities), and 11 SBIR grants. Five cross-cutting indices identify all 472 programs according to principal investigator(s), materials, techniques, phenomena, and environment. Other contents include a bibliographical listing of 43 scientific workshop, topical, descriptive, Research Assistance Task Force, and research facilities reports on select topics that identify materials science research needs and opportunities. Descriptive summary and access information on 14 national user facilities including synchrotron light sources, neutron scattering, electron beam microcharacterization, materials preparation, surface modification, and combustion research; descriptive summary of DOE Center for Excellence for the Synthesis and Processing of Advanced Materials; and an analytical summary of funding levels. To obtain a free copy, contact the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161, or call (301) 903-3427 and request DOE publication DOE/ER-0612P. Copies limited to one per caller while supplies last.
Wall chart, consisting of detailed technical data on properties of silver at cryogenic temperatures, is available free of charge from National Institute of Standards and Technology (NIST). 13 graphs, 4 tables. Included are graphs on temperature dependence of thermal conductivity, specific heat, thermal diffusivity, resistivity, creep coefficient; as well as data on Rockwell hardness, tensile stress, alternating stress, and magnetoresistance. Charts list physical and chemical properties of Ag and change in resistivity of Ag per atomic percent of alloying element, and other properties. Prepared by David R. Smith and F. R. Fickett. To request chart, contact F. R. Fickett, Superconductor and Magnetic Measurements Group, Mail Code 814.05, Electromagnetic Technology Division, Electronics and Electrical Engineering Laboratory, National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80303-3328; e-mail fickett@bldrdoc.gov.
Proceedings: Proceedings of the 1993 Taiwan International Conference on Superconductors held at the Sun-Moon Lake on Aug. 27-30, 1993. Special issue of the Chinese Journal of Physics (Vol. 31, #5). About 70 out of 150 submitted papers are published in this issue. Papers cover the most recent research results in mechanisms and physical properties of superconductors, wires and thin-film devices, and materials synthesis and characterization. Contact the Editorial Office, Chinese Journal of Physics, P.O. Box 23-30, Taipei, Taiwan 10764, Republic of China; telephone and telefax +886 2 363-4923. ---------------------------------------------------------------------
RFP: Interfaces to Superconductors. Joint announcement from the Office of Naval Research and the National Science Foundation. Topic refers to interfaces between high-Tc superconductors and metals, dielectrics, superconductors, and magnetic and optical materials. Research proposals may emphasize any combination of subtopics as long as the thrust of the research is centered on interface-related phenomena. While the long-term Navy interest targets defense and dual-use systems, this announcement is targeted for support of university individual-investigator-type projects to enhance the science base. Must meet guidelines and criteria for support from both agencies. Preproposal must be five pages or less, and include description of the research plans, a cost estimate for a 3-5 year project, brief vitae, and a list of up to 5 closely related publications. Deadline for receipt of preproposals, May 1, 1994. Will be jointly reviewed by NSF/ONR panel. Submit to the Office of Naval Research, Physics Division Code 312, 800 N. Quincy St., Arlington, VA 22217-5660. For information, contact Dr. Donald Liebenberg, at above address; telephone (703) 696-4219 or Dr. David Nelson, Division of Materials Research, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22217-5660; telephone (703) 3061838.
---------------------------------------------------------------------
High-Tc Update is the high-Tc superconductivity information exchange newsletter. Please send 1) preprints, reprints, and other research reports; 2) descriptions of on-going work; 3) meeting announcements and summaries. Your preprint abstracts will be forwarded to OSTI for inclusion in the SIS data base, unless you request otherwise.
The information contained herein is intended for limited distribution. Readers are expected to respect the rights of the authors.
Please address all contributions and inquiries to: Dr. Sreeparna Mitra, A219 Physics, Ames Laboratory/Iowa State University, Ames, Iowa 50011-3020. Telephone: (515) 294-3877. Telefax: (515) 294-1134. Telex: 269266. E-mail: MITRA@AMESLAB.GOV or MITRA@ALISUVAX.BITNET.
Project Director/Editor: Sreeparna Mitra Science Editor: John R. Clem Technical Consultant: Ellen O. Feinberg High-Tc Update, Vol. 8, #9, May 1, 1994. ---------------------------------------------------------------------