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, NSF, and other agencies, organizations, and individuals.
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PLEASE NOTE: Issues of High-Tc Update from November 15, 1993, onward are also available in coded Word versions (BINHEX and RTF). (These versions preserve the Greek letters, special characters, accents, etc.) If you are interested in the alternate formats, 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).
NOTA BENE:
Paramagnetic Meissner Effect Imaged
As reported by J. R. Kirtley (IBM-Yorktown) et al., the spatial distribution of magnetic flux on a granular sample of the high- temperature superconductor Bi2Sr2CaCu2O8+d (Bi-2212) has been imaged within a 480 micrometers x 480 micrometers area using a scanning SQUID microscope. The results establish the presence of local spontaneous orbital magnetic moments, which were suggested to be the origin of the paramagnetic response of these materials in low magnetic fields. The moments apparently are generated by current loops with diameters in the range 10-100 micrometers. The signature of the orbital magnetic moments is a broad distribution of local magnetic fields at the surface of the sample. The authors propose a simple model for the distribution.
Bi Cuprates
As noted by M. R. Norman (Argonne) and H. Ding (Argonne and Illinois- Chicago), photoemission spectra of the high-temperature superconductor Bi2Sr2CaCu2O8+d (Bi-2212) show a dramatic change upon cooling below Tc: the broad peak in the normal state turns into a sharp low-energy peak followed by a higher-binding-energy hump. Recent experiments find that this low-energy peak persists over a significant range in momentum space. The authors show that these data are well described by a simple model of electrons interacting with a collective mode that appears only below Tc.
Detailed in-plane resistivity measurements in Bi-2212 in zero field at temperatures above Tc are reported by S. H. Han et al. (Stockholm). The authors find that the fluctuation conductivity Delta[sigma] is described by the Lawrence-Doniach model with a 2D-3D crossover close to the mean- field critical temperature Tc^[mf]. The c-axis coherence length was found to be 0.9+-0.1 Angstrom.
As reported by Y. Abe et al. (Nagoya), melt-quenched materials consisting of Bi-Sr-Ca-Cu-O with compositions around Bi-2212 and Bi2Sr2CuO6 (Bi-2201) were found to crawl at an extraordinarily high speed up the wall of a metallic copper vessel when the vessel filled with the cast materials was reheated at high temperatures around 850^oC in air. The heat treatment resulted in the formation of a thin superconducting layer on the copper vessel and on the surface of copper wires or plates in contact with the vessel. This effect was found not to occur with Ag, Pt, or other non-copper vessels, or when the copper surfaces were already oxidized. The authors call this phenomenon FFFS (fast flowing and formation of the superconducting phase) and suggest that it has great potential for application to superconductor technologies such as forming complex shapes of superconducting devices.
RBa2Cu3O7-d
The electronic c-axis conductivity sigma_c^[el](omega,T) of Y1- xCaxBa2Cu3O7-d has been studied by C. Bernhard (MPI-Stuttgart) et al. by far-infrared ellipsometry. The replacement of Y^[3+] by Ca^[2+] makes the overdoped regime accessible and decouples the doping state of the CuO2 planes from the oxygenation of the CuO chains. The authors find evidence that the unusual omega and T dependence of sigma_c^[el](omega,T) in the normal state, in particular the pseudogap, is determined by the CuO2 planes, which confine the charge carriers. In the overdoped regime this confinement is relaxed, while in the superconducting state the energy gap is reduced and a large fraction of the quasiparticles remains unpaired.
The Raman scattering spectra of fully oxygenated twin-free YBa2Cu3O7-d crystals have been investigated by M. F. Limonov (SRL-ISTEC) et al. In addition to the out-of-plane and in-plane anisotropy in all A_g-phonon lines in the normal state, pronounced superconductivity-induced xx vs. yy anisotropy has been found in the softening and broadening of the 340 cm^[-1] line below Tc. This suggests either that the chains make a substantial contribution to the superconductivity with a pairing symmetry different from that for the plane, or that the superconducting gap amplitudes are different in the k_x and k_y directions (Delta_x not equal to Delta_y), as expected in the case of a d+s wave gap.
The in-plane (rho_[ab]) and out-of-plane (rho_c) normal-state resistivities of insulating PrBa2Cu3O7-d and superconducting Y0.47Pr0.53Ba2Cu3O7-d (Tc ~~ 18 K) single crystals have been measured by G. A. Levin (Kent State) et al. using a flux transformer method. In the insulating sample the authors found that rho_c/rho_[ab] = a + bT^[-2/3] over two decades of temperature, indicating two-dimensional localization. By suppressing the onset of superconductivity with a magnetic field, the authors observed that low-Tc Y1-xPrxBa2Cu3O7-d is transformed into a 2D insulator with transport properties similar to those of PrBa2Cu3O7-d.
Measurements by S. Uma (MPI-Stuttgart and IIT-Madras) et al. of the specific heat, thermal expansion, neutron diffraction, and magnetic susceptibility of twinned, contamination-free single crystals of PrBa2Cu3O7-d (PBCO) have revealed a peak at T_N^[Pr] = 16.6 K originating from antiferromagnetic ordering of the Pr ion moments. A modest coupling to the Cu(2) spin system also is observed.
As noted by A. V. Dooglav (Kazan State and Orsay) et al., it is widely believed that the long-range antiferromagnetic order in the RBa2Cu3O6+x compounds (R = Y and rare earths except Ce, Pr, and Tb) is totally suppressed for the oxygen index x >= 0.4 (antiferromagnetic insulator- metal transition). The authors present results of Cu(2) NQR/NMR studies of aged RBa2Cu3O7-d (R = Tm, Y) samples showing that magnetic order still can be present for x up to at least 0.7 and at temperatures as high as 77 K.
The effect of columnar defects on the electrical resistivity rho_[bb] and conductivity sigma_[bb] in a superconducting untwinned YBa2Cu3O7-d single crystal has been investigated by J.-T. Kim (KRISS) et al. In low and intermediate magnetic fields, the fluctuation conductivity for the irradiated sample was found to be enhanced and not to exhibit the same 3D-XY scaling behavior found in the unirradiated crystal. In fields above the matching field, however, the signature of 3D-XY scaling was found to appear.
A preprint by E. B. Rudnyi et al. (Moscow State) reports the determination of the Gibbs energy of the YBa2Cu3O6+x phase in the temperature range 250 K to 1300 K from about 3000 experimental points obtained in 220 miscellaneous experiments published in 57 papers. All other thermodynamic properties of the phase, including the conditions for the tetragonal-orthorhombic phase transition and the miscibility gap at lower temperatures, are derived from the Gibbs energy.
As reported by R. Weinstein et al. (TCSUH), the presence of uranium in large-grain melt-textured YBa2Cu3O7-d, even prior to irradiation, improves Jc by over 80%. Irradiation with thermal neutrons to induce fission of the [235]^U component results in further increases in Jc (by a factor of more than 30 at 77 K and 0.25 T, and more than 20 at 50 K and 10 T) to Jc(77K,0.25T) = 2.9 x 10^5 A/cm^2 and Jc(50K,10T) = 1 x 10^6 A/cm^2. However, Tc is reduced by about 0.5 K and the creep rate is increased by about 20%. The authors conclude that the U/n method, still not optimized, already provides attractive results from simple processing changes at low cost.
>From digitized micrographs of melt-textured YBa2Cu3O7-d/Y2BaCuO5 (123/211) composites, N. Vandewalle et al. (Liege) have found that the spatial distribution of the 211 particles is highly inhomogeneous. The authors show that the distribution differences can be explained only by the partial dissolution of the 211 particles during the growth process.
Other Cuprates
As reported by M. Y. Lin et al. (Tamkang), a series of single-phase RBa1.5Sr0.5Cu3Oy (R = La, Nd, Sm, Eu, Gd, Dy, Ho, and Y) compounds with triple-perovskite unit cell has been prepared by the solid-state- reaction method. The Tc of these compounds gradually increases from 52 K to 86 K as the radius of the R ion decreases.
Using field-dependent (0 <= B <= 7 T) noncontact rf surface-resistance measurements, H. A. Blackstead (Notre Dame) et al. have confirmed the onset of granular superconductivity below 23.5 K in the high-temperature superconductor Sm2-xCexCuO4-y (0.15 <= x <= 0.18) at temperatures for which there is no evidence for a bulk Meissner effect.
Two new cubic compounds, GdBa4Cu3O8.5+d (Gd-143, d = 0.68) and DyBa4Cu3O8.5+d (Dy-143, d = 0.6) have been synthesized by Y. T. Zhu et al. (Los Alamos) from precursors Gd2O3, Dy2O3, BaO2, and CuO at 1000^oC in an oxygen atmosphere. SQUID measurements indicated that neither compound is superconductive down to 5 K.
Vortices
The effect of the superconducting gap nodes on the vortex-lattice properties of high-temperature superconductors at very low temperatures has been studied by M.H.S. Amin (UBC) et al. The nonlinear, nonlocal, and nonanalytic nature of this effect is found to have measurable consequences for the vortex-lattice geometry and the effective penetration depth in the mixed state as measured by muon-spin-rotation experiments.
The magnetization curves M(H,T) of the most anisotropic high-temperature superconductors cross at a single point M*(T*), independent of the magnetic field H that is applied perpendicular to the superconducting planes. According to a preprint by A. Junod (Geneve) et al., this property can be derived from the singular part of the free energy of a two-dimensional superconductor with fluctuations at Tc. Correspondingly, three-dimensional superconductors have a crossing point in the quantity M/H^[1/2] near Tc, with an amplitude proportional to the anisotropy ratio gamma = (m_c/m_[ab])^[1/2].
According to a preprint by M.A.R. LeBlanc (Ottawa), the centrifugal force plays the dominant role in dictating the configuration of the electric charges and associated electric field near the vortex core in type-II superconductors in weak magnetic fields.
The self-energy and interaction energy of vacancies and interstitials in the triangular lattice of parallel Abrikosov vortices in type-II superconductors have been calculated by E. Olive and E. H. Brandt (MPI- Stuttgart) using the London theory. The authors investigate various stable and metastable equilibrium configurations of the flux-line lattice around such point defects. The interaction of point defects is weak and can be repulsive or attractive, depending on their type and separation, and on the ratio of the magnetic penetration depth lambda to the average vortex spacing a.
As noted by M. Friesen and P. Muzikar (Purdue), in clean enough samples of the high-Tc oxide materials, the phase transition into the superconducting state occurs along a first-order line in the H-T plane. This means that a two-phase region occurs in the B-T plane, in which the vortex-liquid and vortex-solid phases coexist. The authors discuss the thermodynamics of this two-phase region, developing formulae relating experimental quantities of interest. The authors then apply the 3D-XY scaling theory to the problem, obtaining detailed predictions for the boundaries of the coexistence region. Using published data, the authors are able to predict the width of the two-phase region and determine the physical parameters involved in the 3D-XY description.
The dynamic phase diagram of vortex lattices driven in disorder has been calculated by S. Scheidl (Koeln and Argonne) and V. M. Vinokur (Argonne). The authors use a modified Lindemann criterion for the fluctuations of the distance of neighboring vortices, which unifies previous analytic approaches to the equilibrium and nonequilibrium phase transitions. The temperature shifts of the dynamic melting and decoupling transitions are found to scale inversely proportional to large driving currents. A comparison with two-dimensional simulations shows that the phenomenological approach provides a quantitative estimate for the location of these transitions.
Magnetic-Field Effects
A remarkably complete theory of how magnetic flux penetrates into type- II superconducting circular disks of arbitrary thickness in an axial magnetic field has been developed by E. H. Brandt (MPI-Stuttgart). The author treats the superconductor as a conductor with nonlinear resistivity or with linear complex resistivity. Two preprints describe the results: Part I describes the time-dependent local magnetic fields upon initial flux penetration and subsequent reversal of the applied field, and also includes calculations of magnetization hysteresis loops. Part II describes how to calculate the complex ac susceptibility chi' - ichi" under a variety of conditions. The results may be used to obtain the nonlinear or linear resistivity from contact-free magnetic measurements on superconductors of realistic shape.
The time-dependent magnetic-flux penetration and induced current density in superconducting thin films of rectangular cross section have been computed by C. Ferdeghini (Genova) et al. and compared with measurements in YBCO thin films using a Hall-probe magnetometer.
Exact analytical results have been obtained by T. H. Johansen et al. (Oslo) for the flux-pinning-induced magnetostriction in cylindrical type-II superconductors placed in a parallel magnetic field. In contrast to the circular cylinder, where shape is conserved, the authors found that samples of square cross section should deform with considerable distortion. During a field cycle, both concave, convex, and even more complicated distortions are predicted. The main results are valid for any critical-state model for Jc(B).
As shown by M.A.R. LeBlanc and D.S.M. Cameron (Ottawa), the peaks and valleys observed by E. R. Nowak et al. [Phys. Rev. B54, R12725 (1996)] in the local magnetization M(x) and local relaxation rate S(x) in a single crystal of Tl2Ba2CuO6+d (Tl-2201) containing columnar defects are well reproduced by an empirical model where the critical current density Jc is fractionally enhanced near the matching field B_[phi] and a multiple of B_[phi] by superimposing two broad triangular peaks on a continuous dependence of Jc on the magnetic flux density B.
A preprint by I. Zutic and O. T. Valls (Minnesota) reports the development of a procedure that makes possible the computation of the magnetic-dipole and -quadrupole moments of an anisotropic, unconventional, three-dimensional superconductor. The method, which makes use of the smallness of the ratio of the penetration depth lambda to the sample size d, reduces the required numerical work usually required for such problems.
Analytical tools have been developed by A. Badia and H. C. Freyhardt (Goettingen) to determine the levitation force and the induced screening current arising when a cylindrical magnet approaches a superconducting disk in the Meissner state. The authors also derive a criterion that determines when effective-medium theories are suitable for highly textured granular superconductors.
Thin Films
The quantitative imaging of the sheet resistance of metallic thin films has been accomplished by D. E. Steinhauer et al. (Maryland) by monitoring the frequency shift and quality factor in a resonant scanning near-field microwave microscope. The technique allows fast acquisition of images at approximately 10 ms per pixel over a frequency range from 0.1 to 50 GHz. In the present configuration, the system can resolve changes in sheet resistance as small as 0.6 ohm/square for 100 ohms/square films. See the sheet-resistance image in Fig. 1.
Mesa structures consisting of stacks of intrinsic Josephson junctions on (Bi,Pb)2Sr2Ca2Cu3O10+d thin films have been fabricated by A. Odagawa et al. (Matsushita Electric). The current-voltage (I-V) characteristics along the c axis showed large and distinct hysteresis, a clear multiple- branching structure with a periodic voltage jump, and edge structure, representing the superconducting gap. The estimated superconducting gap value was found to increase for smaller numbers of intrinsic junctions. The thinnest stack exhibited the I-V characteristics of a single junction, and the value of the gap was found to be about 75 meV at 4.2 K. The I-V curve is explained by assuming d_[x^2-y^2] symmetry of the superconducting order parameter without gap suppression.
Pr2-xCexCuO4-y thin films have been fabricated by E. Maiser (Maryland and Karlsruhe) et al. via pulsed laser deposition using N2O reactive gas. The deposition parameters for the films were optimized for each of the 11 investigated Ce concentrations. The optimized thin films show sharp superconducting transitions in ac magnetic susceptibility and electrical resistivity. Ce could be incorporated up to a concentration of x = 0.23 without appearance of impurity phases. The authors also present and discuss the structural properties of their films after a high-temperature post-annealing treatment claimed by M. Brinkmann et al. [Phys. Rev. Lett. 74, 4927 (1995)] to reduce Pr2-xCexCuO4-y single crystals more effectively. Bulk superconductivity was not observed in films with x <= 0.10 under any annealing conditions.
Thin films of La2-xSrxCuO4 (LSCO) and La2CuO4 (LCO) have been grown by H. Sato et al. (NTT) using reactive coevaporation. The authors obtained LSCO thin films on (001) LaSrAlO4 (LSAO) substrates with zero-resistance Tc = 44 K, which is higher than that for bulk samples. A structural analysis indicates that the increase in Tc is due to compressive strain generated by the lattice mismatch. A similar strain effect is suggested from the substrate dependence of Tc for superconducting LCO thin films, for which the zero-resistance Tc reached 50 K on (001) LSAO substrates. The results demonstrate that lattice mismatch with the substrate is an important factor in thin-film growth of LSCO and LCO.
Single-phase PrBa0.7Sr1.3Cu3O7 thin films with the Sr dopant concentration exceeding the solid solubility limit have been epitaxially grown by Y. G. Zhao et al. (Maryland) on (001) SrTiO3 and (001) LaAlO3 substrates using the pulsed-laser-deposition (PLD) method. The resistivity of the doped films grown on LaAlO3 was significantly lower than that of PrBa2Cu3O7, while the resistivity of films grown on SrTiO3 was higher than that of PrBa2Cu3O7. The results were explained by considering the Sr doping effect and the lattice mismatch-induced strain effect. The authors stress that this work shows the potential of PLD to grow single-phase films with the dopant concentration exceeding the solid solubility limit.
The development of a technique for growing CoSi2 buffer layers on Si for subsequent growth of YBCO films is reported by I. Belousov (Kiev) et al. Heterostructures of YBCO/CoSi2/Si and YBCO/CeO2/YSZ/CoSi2/Al2O3 were grown with YBCO Tc's up to 86 K.
Measurements and modeling of the microwave-frequency (rf) power dependence of the impedance in YBCO thin-film grain-boundary Josephson junctions have been carried out by Y. M. Habib (MIT, Lincoln Laboratory, and Rome Laboratory) et al. Using a stripline resonator with an engineered grain-boundary Josephson junction, the authors performed microwave impedance measurements as a function of rf current (10^[-4] to 1 A) and temperature (5 to 70 K). To understand the observed power dependence, the authors used a long-junction model consisting of a parallel array of inductively coupled resistively shunted junctions. The impedance calculated using the long-junction model fits the measured data qualitatively.
An unconventional technique for the measurement of magnetic relaxation in superconducting films at short times (~10^[-4] s) is described in a paper by S. O. Valenzuela (Buenos Aires) et al. The technique combines the application of a pulsed magnetic field and a synchronized high- energy pulsed laser. The authors report remanent magnetic relaxation in (Y,Gd)Ba2Cu3O7-d thin films over five decades in time at reduced temperatures T/Tc > 0.8.
Applications
The performance of an integrated hybrid magnetometer consisting of a thin-film YBCO high-Tc superconducting magnetic pick-up system and a Bi Hall detector is reported by G. Kaiser et al. (Jena). The authors carried out sensitivity measurements in the temperature range between 70 K and 300 K and found that the sensitivity increased by a factor of about 100 below the transition temperature of the pick-up system, as expected from a calculation of the field amplification. At 77 K, the authors measured a resolution of 8 pT/sqrt[Hz] in the white-noise range (>0.6 kHz). The noise at frequencies less than 100 Hz was dominated by laboratory background.
Josephson junctions and dc SQUIDs on Si bicrystal substrates with epitaxially grown 24 degrees YBCO grain boundaries have been investigated by F. Schmidl et al. (Jena). The YBCO thin films, YSZ and CeO2 buffer layers, and passivation/contact layers were all prepared by laser deposition. The authors report that dc SQUIDs with transfer functions up to 30 microvolts/phi_0 and white-noise levels of 30 mu[phi_0]/sqrt[Hz] were realized.
Coherent behavior (phase-locking) in a system of two superconducting loops containing arrays of Josephson junctions and interacting via mutual inductance has been modeled by A. N. Grib (Jena and Kharkov State) et al. The authors find under certain conditions that the mutual inductance between loops can produce total phase-locking of the system.
Theory
A paper by D. Coffey (SUNY-Buffalo) addresses the need to incorporate long-range Coulomb correlations, as well as the short-range correlations responsible for the magnetic behavior, in any description of superconductivity in the cuprates. The author stresses that the long- range Coulomb interaction is responsible for the magnitude of the corrections to the mean-field treatment of superconductivity which have been seen in both tunneling and ARPES experiments and probably has a strong influence on the magnitude of the gap and Tc.
A preprint by S. Dorbolo et al. (Liege) reports calculations of the mean-field electronic specific heat of a superconductor in the presence of a magnetic field. The authors assume an energy spectrum with saddle points in the band structure, corresponding to Van Hove singularities in the density of states. From an analysis of the electronic specific heat in YBa2Cu3O7-d, HgBa2Ca2Cu3O8+d (Hg-1223), and Tl2Ba2CuO6+d (Tl-2201) near Tc, the authors find confirmation of the existence of d-wave symmetry of the energy gap parameter, and they find evidence for the presence of Van Hove singularities.
According to T. P. Devereaux (George Washington) et al., the buckling of the CuO2 planes in certain cuprates can be due to the electric field across the planes induced by different atoms above and below. The buckling is accompanied by a strong coupling of the out-of-phase B_[1g] vibration of the oxygen atoms to the electrons. The electric field can be deduced from Raman results on YBa2Cu3O6+x and Bi2Sr2(Ca1-xYx)Cu2O8 with different O and Y doping, respectively. In the latter case, the symmetry breaking by replacing Ca partially by Y enhances the coupling by an order of magnitude.
As noted by F. Guinea (Madrid), lattice distortions in which the axes are locally rotated provide an intrinsic source of frustration in anisotropic superconductors. The author presents a general framework to study this effect, and also discusses the influence of lattice defects and phonons in d-wave and s+d layered superconductors.
A preprint by A. S. Alexandrov and R. T. Giles (Loughborough) proposes a simple analytical form of the partition function for charged bosons localized in a random potential and derives the resulting thermodynamics below the superfluid transition temperature. In the low-temperature limit, the specific heat C depends on the localization-length exponent nu: C is linear for nu <= 1, but for nu > 1, the authors obtain C proportional to T^[1/nu]. This unusual sublinear temperature dependence of the specific heat has recently been observed in La2-xSrxCuO4 below Tc.
According to a paper by E. L. Haase (Karlsruhe), the mechanism for superconductivity in both conventional and high-temperature superconductors is the electron-phonon mechanism, enhanced through large-amplitude fluctuations because of proximity to nearby structural phase transitions.
Other Activities
Measurements of the upper critical field H_[c2](T) of LuNi2B2C and YNi2Bi2C single crystals with low impurity scattering rates have been carried out by S. V. Shulga (Dresden) et al. The authors quantitatively explain the observed temperature dependence of H_[c2](T), including positive curvature, using an effective two-band model.
A preprint by G. Heine (Wien) and W. Lang (Rochester) reports measurements of the resistance and magnetoresistance of a new ceramic thin-film temperature sensor (Cernox-1080, Lake Shore Cryotronics) in magnetic fields up to 13 T in the temperature range 4.2 to 300 K. The authors describe how to correct apparent temperature reading errors of the Cernox thermometer in high magnetic fields.
A method called the half-scan technique is proposed by G. Ravikumar (BARC-Mumbai) et al. for determining magnetization hysteresis loops using the Quantum Design Magnetic Property Measurement System (MPMS). The authors report that this technique circumvents problems caused by field inhomogeneity. In the peak-effect regime of superconducting CeRu2 and 2H-NbSe2, the authors found that the magnetization hysteresis using the half-scan technique was significantly larger than that obtained using conventional MPMS measurements.
Measurements of the normal-state in-plane and out-of-plane magnetoresistance (MR) of single crystals of the layered perovskite superconductor Sr2RuO4 (Tc ~~ 1 K) are reported by N. E. Hussey (IRC- Superconductivity) et al. The authors find evidence for the existence of two separate contributions to the c-axis MR over a wide temperature range.
The use of field emission to determine the superconducting energy gap is analyzed in a preprint by G. A. Gogadze (Kharkov) et al.
Overviews
The spin-fluctuation model for high-temperature superconductivity has been reviewed by D. Pines (Illinois-Urbana). The author describes how this model explains the anomalous results of transport, magnetotransport, optical, Raman, and ARPES measurements in the normal state of both underdoped and overdoped cuprates and makes an unambiguous prediction of the d_[x^2-y^2] pairing state. In this model, the planar quasiparticles are best described as a nearly antiferromagnetic Fermi liquid, a system whose properties differ in almost every way from the Landau Fermi liquids found in conventional superconductors. The mechanism for high Tc is spin-fluctuation exchange, an electronic mechanism, which produces a quasiparticle interaction mirroring the dynamic spin susceptibility measured in NMR experiments (55 refs.).
The topic of keV - MeV ion implantation into YBa2Cu3O7-d (YBCO) thin film/substrate combinations and bulk oxide samples has been reviewed by J. A. Kilner (Imperial) and Y. P. Li (Imperial and TCSUH). The authors focus on 50 keV [2]^H+ implantation (10^[12]/cm^2 and 10^[16]/cm^2), 200 keV O+ implantation (10^[12] [16]^O/cm^2, 5 x 10^[14] [18]^O/cm^2, and 5 x 10^[16] [18]^O/cm^2), 200 keV [20]^Ne+ implantation (5 x 10^[14]/cm^2), and 1.5 MeV [197]^Au+ implantation (5 x 10^[15]/cm^2) at room temperature. The authors also note that ion implantation is a useful way to determine diffusion coefficients in YBCO thin films (55 refs.).
An overview of the electrical conductivity and thermopower of different materials has been prepared by A. B. Kaiser (Victoria University of Wellington). Included are discussions of glassy metals, conducting polymers, high-Tc and conventional superconductors, spin-fluctuation metals (including chromium), giant and colossal magnetoresistance materials, and carbon nanotubes (47 refs.).
A preprint by D. Rainer (Bayreuth) et al. uses the Fermi-liquid theory of superconductivity to study the implications of particle-hole coherence on properties of d-wave superconductors near surfaces. Resulting surface phenomena are suppression of the superconducting order parameter, surface bound states associated with Andreev reflection, anomalous screening currents, and spontaneous breaking of time-reversal symmetry. The authors review these phenomena and present new results for the effects of surface roughness (30 refs.)
A brief overview of (a) the advancement of Tc since Bednorz and Mueller's discovery of cuprate superconductivity, (b) the discovery of new high-Tc materials without volatile toxic elements, and (c) the prospects for high Tc has been prepared by C. W. Chu (TCSUH) (22 refs.).
A preprint by H. Ding (Argonne and Illinois-Chicago) et al. reviews ARPES results on the superconducting gap and the pseudogap in Bi2Sr2CaCu2O8+d. Optimally and overdoped samples exhibit a d-wave gap, which closes at the same temperature Tc for all k points. In underdoped samples, a leading edge gap is found up to a temperature T* > Tc. The authors find that T* scales with the maximum low-temperature gap, increasing as the doping is reduced. The k dependence of the pseudogap is similar to that of the superconducting gap, except that the pseudogap closes at different temperatures for different k points (13 refs.).
Contributed by John R. Clem
Contents: Technology News is on page 7; Preprints begin on page 7; Coming Events begin on page 14; and a figure referred to in Nota Bene is on page 15.
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.
TECHNOLOGY NEWS (Also see Applications section of Nota Bene.)
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 and engineers at the Naval Research Laboratory (NRL) and the Naval Surface Warfare Center (NSWC) - Carderock Division - have set a new record in superconductive motor performance using high-Tc superconducting field magnets. The motor produced an output of 104 hp with its high-Tc field windings cooled to 77 K (previous known record was 5 hp). At a field winding temperature of 28 K (liquid neon), the motor produced 230 hp of shaft power and at a temperature of 4.2 K (liquid helium), it produced 320 hp.
The motor is a dc homopolar or acyclic machine, a fundamental property of which is that there are no forces developed on the field winding of the motor in reaction to the electromagnetically induced torque in its armature (rotor). This property, therefore, reduces the design complexity of the superconducting magnets (both low Tc and high Tc) and the suspension components to structurally support the magnets in the machine. The field magnet for the motor consisting of six discrete coils wound with Bi-2223 wire was fabricated by American Superconductor Corp. to specifications developed by NRL and NSWC.
In addition to the use of superconducting magnets, the NSWC homopolar motor employs advanced current collectors or brushes which were designed and developed at NSWC, and employ sodium potassium liquid metal to transfer electric current from the stator of the machine to its rotating armature. Liquid-metal current collectors have the advantage of being able to operate very efficiently at high current and for the results reported here, the current collectors of the homopolar machine performed reliably at values of electrical current in excess of 4 x 10^4 A.
The motor demonstration may have direct impact on ongoing Navy programs in minesweeping, electric drive, and superconductive magnet-energy- storage (SMES) devices. Other potential benefits include applications in transportation, electric power transmission and distribution, magnetic resonance imaging, and other medical devices. NRL has been responsible for the development and testing of HTS conductors used in the magnets.
Plans for the future are to continue to use the NSWC homopolar motor as a test bed for high-Tc superconducting magnets. Currently the high-Tc field winding is being redesigned and modified to be cooled using a cryocooler refrigerator. When completed, this facility will provide the capability to measure the performance of high-Tc field windings over a broad range of temperatures.
Contributed by Sreeparna Mitra
PREPRINTS To obtain a particular preprint, contact the first author at the address given at the end of the citation. Help us expand this list by sending us your complete preprint. Please specify where and when your paper was submitted. An * next to an entry indicates it is a correction or revision of a previous entry. PACS codes and/or key words are given at the end of the citation.
A. Abdesselam and V. Rivasseau, "Explicit Fermionic Tree Expansions." Centre de Physique Theorique, CNRS UPR 14, Ecole Polytechnique, F-99128 Palaiseau Cedex, FRANCE; V. Rivasseau's e-mail rivass@orphee.polytechnique.fr; preprint also available at cond- mat@xxx.lanl.gov (#9712055).
Yoshihiro Abe, Taisuke Harada, Koichi Nakaya, and Masayuki Nogami, "Fast Flowing and Formation of Superconducting Bi2Sr2Ca1Cu2Ox Layers on Metallic Copper Wires and Plates." To be published in Physica C (in press). Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, JAPAN; telephone +81 52 735 5278; telefax +81 52 735 5278; e-mail abe@mse.nitech.ac.jp.
A. S. Alexandrov and R. T. Giles, "Low Temperature Thermodynamics of Charged Bosons in a Random Potential and the Specific Heat of La2- xSrxCuO4 Below Tc." Submitted to Phys. Rev. B. Department of Physics, Loughborough University, Loughborough LE11 3TU, UNITED KINGDOM; e-mail a.s.alexandrov@lboro.ac.uk; R. T. Gile's telephone +44 1509-223315 or -228409; telefax +44 1509 223986; e-mail r.t.giles@lboro.ac.uk; preprint also available at cond-mat@xxx.lanl.gov (#9712029). 74.20.-z.
M.H.S. Amin, Ian Affleck, and M. Franz, "Low Temperature Behavior of the Vortex Lattice in Unconventional Superconductors." Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC, CANADA V6T 1Z1; telephone (604) 822-2238; telefax (604) 822-5324; e-mail amin@magnon.physics.ubc.ca; preprint also available at cond-mat@xxx.lanl.gov (#9712218).
T. Aouaroun, V. Hardy, and Ch. Simon, "Plastic Vortex Creep in the High- Tc Superconductor (Tl2/3,Bi1/3)Sr2CaCu2Ox." To be published in Physica C (in press). Laboratoire CRISMAT, UMR 6508 associee au CNRS, ISMRA et Universite de Caen, 6 Boulevard du Marechal Juin, F-14050 Caen Cedex, FRANCE; telefax +33 2 31 45 26 86; e-mail physol@crismat.ismra.fr.
S. N. Artemenko and A. F. Volkov, "Collective Oscillations in Superconductors Revisited." Institute for Radioengineering and Electronics of the Russian Academy of Sciences, Moscow, RUSSIA; e-mail art@mail.cplire.ru; preprint also available at cond-mat@xxx.lanl.gov (#9712086).
A. Badia and H. C. Freyhardt, "Meissner State Properties of a Superconducting Disk in a Non-Uniform Magnetic Field." To be published in J. Appl. Phys. Dpto. Fisica de la Materia Condensada, Centro Politecnico Superior, c/Maria de Luna 3, E-50015 Zaragoza, SPAIN; e-mail anabadia@posta.unizar.es. 74.25.Ha; 85.25.Ly; 74.72.-h; 02.30.Qy.
I. Belousov, E. Rudenko, S. Linzen, and P. Seidel, "Local Nucleation and Lateral Crystallization of Silicide Cobalt Phases at Interaction of Cobalt Film with Silicon Surface." Submitted to Thin Solid Films. Institute of Metal Physics, Ukrainian National Academy of Sciences, Vernadskii Ave. 36, 252180 Kiev, UKRAINE; P. Seidel's telephone at Friedrich-Schiller-Universitaet Jena in Jena, Germany +49 3641 947410; telefax +49 3641 947412; e-mail seidel@ifk.uni-jena.de. Key words: cobalt silicide, lateral crystal growth, buffer layer, YBa2Cu3O7-x.
C. Bernhard, R. Henn, A. Wittlin, M. Klaeser, Th. Wolf, G. Mueller-Vogt, C. T. Lin, and M. Cardona, "The Electronic c-Axis Response of Y1- xCaxBa2Cu3O7-d Crystals Studied by Far-Infrared Ellipsometry." To be published in Phys. Rev. Lett. Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; telephone +49 711 689 1733; telefax +49 711 689 1010; e-mail bernhard@cardix.mpi-stuttgart.mpg.de. 78.30.-j; 74.25.Gz; 78.20.Ci; 74.72.Bk.
H. A. Blackstead, R. F. Jardim, P. Beeli, D. B. Pulling, and A. K. Heilman, "Observation of Granular Superconductivity in Polycrystalline Sm2-xCexCuO4-y." To be published in Phys. Rev. B (in press). Department of Physics, University of Notre Dame, Notre Dame, IN 46556; telephone (219) 631-6386. 74.80.Bj.
Ernst Helmut Brandt, "Superconductor Disks and Cylinders in Axial Magnetic Field: I. Flux Penetration and Magnetization Curves." Submitted to Phys. Rev. B. Institut fuer Physik, Max-Planck-Institut fuer Metallforschung, D-70506 Stuttgart, GERMANY; telephone +49 711 689 1823; telefax +49 711 689 1010; e-mail ehb@physix.mpi-stuttgart.mpg.de. 74.60.-w; 74.60.Ge.
Ernst Helmut Brandt, "Superconductor Disks and Cylinders in Axial Magnetic Field: II. Nonlinear and Linear ac Susceptibilities." Submitted to Phys. Rev. B. Institut fuer Physik, Max-Planck-Institut fuer Metallforschung, D-70506 Stuttgart, GERMANY; telephone +49 711 689 1823; telefax +49 711 689 1010; e-mail ehb@physix.mpi-stuttgart.mpg.de. 74.60.-w; 74.60.Ge.
B. Buffeteau, T. Hargreaves, B. Grevin, and C. Marin, "Oxygen Dependence on Superconducting Properties of La1.85Sr0.15CuO4-d Ceramic and Crystal Samples." To be published in Physica C (in press). Departement de Recherche Fondamentale sur la Matiere Condensee, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, FRANCE; telephone +33 4 7688 4243; e-mail buffetea@drfmc.ceng.cea.fr. Key words: La2-xSrxCuO4-d, d- wave superconductors, oxygen stoichiometry, specific heat, NQR.
C. W. Chu, "A Decade of High Temperature Superconducting Materials." Preprint #97:159; to be published in the Proc. of the 10th Int. Symp. on Supercond. (ISS'97), Gifu, Japan, Oct. 27-30, 1997. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu. Key words: high-temperature superconductivity, high-temperature superconducting materials, high- temperature superconductivity history.
D. Coffey, "Strong-Coupling Features Due to Quasiparticle Interactions in Two Dimensional Superconductors." Submitted to Phys. Rev. B. Department of Physics, State University of New York, 239 Fronczak Hall, Buffalo, NY 14260-1500; telephone (716) 645-2017; telefax (716) 645- 2507; e-mail dcoffey@acsu.buffalo.edu; Web site http://www.physics.buffalo.edu; preprint also available at cond- mat@xxx.lanl.gov (#9712088).
A. N. Das, Joydev Lahiri, and S. Sil, "Superconducting Gap Ratio and Isotope-Shift Exponent in a Pair-Tunneling Model." To be published in Physica C (in press). Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064, INDIA; telefax +91 33 337 4637; e-mail atin@hpl.saha.ernet.in. Key words: interlayer pairing, phase diagram, isotope effect. 74.20.-z; 74.62.-c; 76.62.Dh.
T. P. Devereaux, A. Virosztek, A. Zawadowski, M. Opel, P. F. Mueller, C. Hoffmann, R. Philipp, R. Nemetschek, R. Hackl, A. Erb, E. Walker, H. Berger, and L. Forro, "Physical Origin of the Buckling in CuO2: Electron-Phonon Coupling and Raman Spectra." Department of Physics, George Washington University, Washington, DC 20052; e-mail tpd@gwis2.circ.gwu.edu; preprint also available at cond-mat@xxx.lanl.gov (#9712128). 74.72.-h; 63.20.Kr; 78.20.Bh; 71.10.-w.
H. Ding, J. C. Campuzano, M. R. Norman, M. Randeria, T. Yokoya, T. Takahashi, T. Takeuchi, T. Mochiku, K. Kadowaki, P. Guptasarma, and D. G. Hinks, "ARPES Study of the Superconducting Gap and Pseudogap in Bi2Sr2CaCu2O8+x." To be published in J. Phys. Chem. Solids: Proc. of the Conf. on Spectroscopies in Novel Supercond. (SNS'97), Cape Cod, Mass., Sept. 14-18, 1997. Materials Sciences Division-223, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telephone (630) 252-5018; telefax (630) 252-7777; e-mail hongding@uic.edu; preprint also available at cond-mat@xxx.lanl.gov (#9712100).
A. V. Dooglav, H. Alloul, O. N. Bakharev, C. Berthier, A. V. Egorov, M. Horvatic, E. V. Krjukov, P. Mendels, Yu. A. Sakhratov, and M. A. Teplov, "Cu(2) Nuclear Resonance Evidence for an Original Magnetic Phase in Aged 60 K-Superconductors RBa2Cu3O6+x (R=Tm, Y)." Submitted to Phys. Rev. B. Contact M. A. Teplov, Magnetic Resonance Laboratory, Kazan State University, 420008 Kazan, RUSSIA; e-mail mikhail.teplov@ksu.ru; preprint also available at cond-mat@xxx.lanl.gov (#9712035).
S. Dorbolo, M. Ausloos, and M. Houssa, "Electronic Specific Heat of a Superconductor with Van Hove Singularities: Effect of a Magnetic Field." To be published in Phys. Rev. B. SUPRAS, Institute of Physics B5, University of Liege, B-4000 Liege, BELGIUM; M. Ausloos' telephone +32 4 366 5249. 74.25.Bt; 74.60.Ec; 74.72.-h.
Yu. Eltsev and OE. Rapp, "Out-of-Plane Hall Effect in YBa2Cu3O7-d: Vortex-Glass Behavior and Scaling of c-Axis and Hall Resistivities." To be published in Phys. Rev. B. Department of Solid State Physics, Kungliga Tekniska Hoegskolan, SE-100 44 Stockholm, SWEDEN. 74.72.Bk; 74.60.Ge; 72.15.Gd.
C. Ferdeghini, E. Giannini, G. Grassano, D. Marre, I. Pallecchi, and A. S. Siri, "Magnetic Flux Penetration and Current Density in Superconducting Thin Films." To be published in Physica C (in press). INFM/CNR, Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova, ITALY; telephone +39 10 353 6323; telefax +39 10 311066. Key words: critical current density, mixed state, thin films.
Mark Friesen and Paul Muzikar, "Two-Phase Region of the Vortex-Solid Melting Transition: 3D XY Theory." Department of Physics, Purdue University, West Lafayette, IN 47907-1396; telephone (765) 494-3045; telefax (765) 494-0706; e-mail friesen@physics.purdue.edu; preprint also available at cond-mat@xxx.lanl.gov (#9712214). 74.25.Dw; 74.60.Ec; 64.60.Fr.
G. A. Gogadze, V. M. Svistunov, R. Aoki, H. Murakami, and M. Shirai, "A New Method of Superconducting Energy Gap Spectroscopy." To be published in Physica C. B. Verkin Institute for Low Temperature Physics and Engineering of the Ukrainian Academy of Sciences, 310164 KharUkov, UKRAINE; telefax +380 572 322370; e-mail gogadze@ilt.kharkolv.ua. Key words: field emission, energy gap, distribution function, gap spectroscopy. 74.25.-q; 79.70.+q.
A. N. Grib, P. Seidel, and M. Darula, "The Threshold of Phase Locking in the System of Two Multi-Junction Superconducting Loops." Submitted to J. Low Temp. Phys. Institut fuer Festkoerperphysik, Friedrich-Schiller- Universitaet Jena, D-07743 Jena, GERMANY; P. Seidel's telephone +49 3641 947410; telefax +49 3641 947412; e-mail seidel@ifk.uni-jena.de. 85.25.Dq; 74.50.+r.
F. Guinea, "Intrinsic Frustration Effects in Anisotropic Superconductors." Instituto de Ciencia de Materiales, Consejo Superior de Investigaciones Cientificas, Cantoblanco, E-28049 Madrid, SPAIN; preprint also available at cond-mat@xxx.lanl.gov (#9711221). 73.40.Gk; 74.20.Mn; 74.72.-h.
Ernst L. Haase, "On the Thermodynamics of HTS: The Coupling of the Superconducting to One or Two Structural Phase Transitions Strongly Enchances Tc." Presented at the 5th Int. Symposium on Adv. Mater., Islamabad, Pakistan, Sept. 21-25, 1997; to be published in Adv. Mater. Forschungszentrum Karlsruhe, IMF III, D-76021 Karlsruhe, GERMANY; telephone +49 7247 82 2807; telefax +49 7247 82 3956; e-mail haase@imf.fzk.de.
Y. M. Habib, C. J. Lehner, D. E. Oates, L. R. Vale, R. H. Ono, G. Dresselhaus, and M. S. Dresselhaus, "Measurements and Modeling of the Microwave Impedance in High-Tc Grain-Boundary Josephson Junctions: Fluxon Generation and rf Josephson Vortex Dynamics." Submitted to Phys. Rev. B. Contact D. E. Oates, Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, MA 02173-9108; telephone (781) 981-4707; telefax (781) 981-5328; e-mail oates@ll.mit.edu. 74.25.Nf; 74.50.+r; 74.76.Bz.
S. H. Han, Yu. Eltsev, and OE. Rapp, "Resistive Transition and Fluctuation Conductivity in Bi2Sr2CaCu2O8+d Single Crystals." To be published in Phys. Rev. B. Department of Solid State Physics, Kungliga Tekniska Hoegskolan, SE-10044 Stockholm, SWEDEN.
G. Heine and W. Lang, "Magnetoresistance of the New Ceramic 'Cernox' Thermometer from 4.2 K to 300 K in Magnetic Fields Up to 13 T." To be published in Cryogenics. Institut fuer Materialphysik der Universitaet Wien and Ludwig Boltzmann Institut fuer Festkoerperphysik, Kopernikusgasse 15, A-1060 Wien, AUSTRIA; telephone +43 1 586 3408 20; telefax +43 1 586 3408 13; W. Lang's e-mail wolfgang.lang@univie.ac.at. Key words: thermometry, high magnetic fields, magnetoresistance.
Masahiko Hiratani, Yoshinobu Tarutani, and Kazumasa Takagi, "Lattice Bending Appearing in Transmission Electron Microscope View: The Strain Release in the Heteroepitaxial Structure of the HoBa2Cu3Oy/PrBa2Cu3Oy/SrTiO3 (110) Substrate." To be published in Physica C (in press). Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo 185, JAPAN. Key words: heteroepitaxy, strain, superconductor, S-N-S junction.
Y. T. Huang, D. S. Shy, and L. J. Chen, "Phase Evolution of Co- Precipitated Bi-Pb-Sr-Ca-Cu-O Powder." To be published in Physica C (in press). Contact D. S. Shy, Materials Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu 310, Taiwan, REPUBLIC OF CHINA. Key words: Bi-2223, co-precipitation, phase evolution, kinetics.
N. E. Hussey, A. P. Mackenzie, J. R. Cooper, Y. Maeno, S. Nishizaki, and T. Fujita, "The Normal State Magnetoresistance of Sr2RuO4." To be published in Phys. Rev. B. Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106, JAPAN; telephone +81 3 3478 6811, ext. 5663; telefax +81 3 3478 7698; e-mail nehussey@troy.issp.u-tokyo.ac.jp. 72.15.Eb; 72.15.Gd; 74.25.Fy; 74.70.- b; 74.72.-h.
Kazuyuki Isawa, Yuji Yaegashi, Seiya Ogota, Mitsugu Nagano, Shiroshi Sudo, Kazuyoshi Yamada, and Hisao Yamauchi, "Thermoelectric Power of Delafossite-Derived Compounds: RCuO2+d (R=Y, La, Pr, Nd, Sm, and Eu)." To be published in Phys. Rev. B. Research and Development Center, Tohoku Electric Power Co., Inc., 2-1 Nakayama 7-chome, Aoba-ku, Sendai 981, JAPAN; telephone +81 22 278 0356; telefax +81 22 278 2176. 72.20.- i; 75.20.Hr.
M. H. Iversen, J.-E. Jorgensen, and N. H. Andersen, "Charge Localization in Oxidized Pb2Sr2Y0.5Ca0.5Cu3O8+d Studied by Electron and Neutron Powder Diffraction." To be published in Physica C (in press). Contact J.-E. Jorgensen, Department of Chemistry, University of Arhus, DK-8000 Arhus C, DENMARK; telephone +45 8942 3333; telefax +45 8619 6199; e-mail jenserik@kemi.aau.dk. Key words: neutron diffraction, electron diffraction, charge localization and superconductivity.
T. H. Johansen, J. Lothe, and H. Bratsberg, "Shape Distortion by Irreversible Flux-Pinning-Induced Magnetostriction." Submitted to Phys. Rev. Lett. Department of Physics, University of Oslo, P.O. Box 1048, Blindern, 0316 Oslo 3, NORWAY; e-mail t.h.johansen@fys.uio.no; preprint also available at cond-mat@xxx.lanl.gov (#9712091). 74.25.Ha; 74.60.Ge; 74.60.Jg.
Alain Junod, Jean-Yves Genoud, Gilles Triscone, and Tony Schneider, "Crossing Point of the Magnetization in High-Temperature Superconductors." To be published in Physica C (in press). Departement de Physique de la Matiere Condensee, Universite de Geneve, 24 quai Ernest-Ansermet, CH-1211 Geneve 4, SWITZERLAND; telephone +41 22 702 6204; telefax +41 22 702 6869; e-mail alain.junod@physics.unige.ch. Key words: magnetization, high-temperature superconductors, fluctuation effects, critical phenomena.
A. B. Kaiser, "Transport in Novel Materials." To be published in Physics of Novel Materials, edited by M. P. Das (World Scientific, Singapore, 1998). Department of Physics, Victoria University of Wellington, P.O. Box 600, Wellington, NEW ZEALAND; telephone +64 4 471 5347; telefax +64 4 495 5237; e-mail alan.kaiser@vuw.ac.nz.
G. Kaiser, S. Linzen, H. Schneidewind, U. Huebner, and P. Seidel, "First Experimental Investigations on a Thin Film Hall Magnetometer with a High Temperature Superconducting Pick-up Antenna." Submitted to Cryogenics. Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena, GERMANY; telephone +49 3641 947416; telefax +49 3641 947412; e-mail ouk@rz.uni-jena.de. Key words: magnetometer, high-temperature superconductor, Hall effect, sensitivity, resolution.
Jeffrey Kane, K.-W. Ng, and D. Moecher, "Effects of Lead Doping on Tc and Energy Gap of Bi2Sr2CaCu2O8 by Tunneling Spectroscopy." To be published in Physica C (in press). Contact K.-W. Ng, Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055; telephone (606) 257-6722; telefax (606) 323-2846. Key words: energy gap, tunneling spectroscopy, substitution effects.
J. A. Kilner and Y. P. Li, "Ion Implantation and Mass Transport in YBa2Cu3O7-d Films and Substrates." Preprint #97:165; submitted to the Proc. of the European Conf. on Accelerators in Appl. Res. and Technol., Eindhoven, The Netherlands, Aug. 25-30, 1997; to be published in Phys. Research B. Department of Materials, Imperial College of Science Technology and Medicine, London SW7 2BP, UNITED KINGDOM; preprint also available from Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu.
Jin-Tae Kim, Y. K. Park, J.-C. Park, H. R. Lim, S. Y. Shim, D. H. Kim, W. N. Kang, J. H. Park, T. S. Hahn, S. S. Choi, W. C. Lee, J. D. Hettinger, and K. E. Gray, "Pinning Effect on Fluctuation Conductivity in a Superconducting Untwinned YBa2Cu2O7-d Single Crystal with Columnar Defects." Submitted to Phys. Rev. B. Superconductivity Group, Korea Research Institute of Standards and Science, P.O. Box 102, Yusong, Taejon 305-600, KOREA; preprint also available from Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov. 74.60.Ge; 74.60.Ec; 74.40.+k.
Weon-Ju Kim, Sun-Chil Kwon, Ho Jin Lee, Hee-Gyoun Lee, Gye-Won Hong, and Il-Hyun Kuk, "Mechanical Grinding of Precursor Powder and Its Effect on the Microstructure and Critical Current Density of Ag/Bi-2223 Tapes." To be published in Physica C (in press). Superconductivity Research Laboratory, Korea Atomic Energy Research Institute, P.O. Box 105, Taejon 305-600, SOUTH KOREA; telephone +82 42 868 8026; telefax +82 42 862 5496; e-mail weonjkim@nanum.kaeri.re.kr. Key words: Ag/Bi-2223 tapes, particle size reduction, amorphization.
J. R. Kirtley, A. C. Mota, M. Sigrist, and T. M. Rice, "Magnetic Imaging of the Paramagnetic Meissner Effect in the Granular High-Tc Superconductor Bi2Sr2CaCu2Ox." To be published in J. Phys. Cond. Mat. IBM Thomas J. Watson Research Center, P.O. Box 218, Route 134, Yorktown Heights, NY 10598; telephone (914) 945-2043; telefax (914) 945-4421; e- mail kirtley@watson.ibm.com; preprint also available at cond- mat@xxx.lanl.gov (#9712113).
S. Kolesnik, A. Vostner, G. Brandstaetter, H. W. Weber, F. M. Sauerzopf, and B. W. Veal, "Interplay Between Pinning by Point Defects and Twin Planes in Oxygen Deficient YBa2Cu3Ox Crystals." Presented at the 10th Int. Symp. on Supercond. (ISS'97), Gifu, Japan, Oct. 27-30, 1997; to be published in Adv. in Supercond. Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warszawa, POLAND; telephone +48 22 843 5324; telefax +48 22 843 0926; e-mail koles@ifpan.edu.pl. Key words: YBa2Cu3Ox crystals, oxygen deficiency, twin planes, flux pinning.
M. Kuhn, B. Schey, R. Klarmann, W. Biegel, B. Stritzker, J. Eisenmenger, and P. Leiderer, "Patterning of YBCO Thin Films by Ion Implantation and Magneto-Optical Investigations." To be published in Physica C (in press). Institut fuer Physik, Universitaet Augsburg, D-86135 Augsburg, GERMANY; telephone +49 821 598 3403; telefax +49 821 598 3405; e-mail kuhn@physik.uni-augsburg.de. Key words: applications of high-Tc superconductors, thin films, irradiation effects, ion implantation, magneto-optical. 85.70.Sq.
Th. Lang, D. Buhl, and L. J. Gauckler, "Influence of the Maximum Temperature During Partial Melt-Processing of Bi-2212 Thick Films on Microstructure and Jc." To be published in Physica C (in press). Department of Materials, ETH Zurich, Swiss Federal Institute of Technology, CH-8092 Zurich, SWITZERLAND; telephone +41 1 632 56 51; telefax +41 1 632 11 32; e-mail lang@nonmet.mat.ethz.ch. Key words: Bi2Sr2CaCu2Ox, high-temperature superconductor, partial melt processing, maximum processing temperature, critical current density.
M.A.R. LeBlanc, "Charged Vortices in High Temperature Superconductors: Role of the Centrifugal and Lorentz Forces." To be published in Supercond. Sci. & Technol. Department of Physics, University of Ottawa, Ottawa, Ontario, CANADA K1N 6N5; telefax (613) 562-5190; e-mail 76153.2047@compuserve.com. 74.60.Ge; 75.72.-h.
M.A.R. LeBlanc and Daniel S.M. Cameron, "Vortex Localization in Single Crystals of Tl2Ba2CuO6+d with Columnar Defects: An Empirical Model." To be published in Phys. Rev. B. Department of Physics, University of Ottawa, Ottawa, Ontario, CANADA K1N 6N5; telefax (613) 562-5190; e-mail 76153.2047@compuserve.com. 74.60.Ge; 74.60.Jg; 74.72.Fq; 74.25.Ha.
G. A. Levin, T. Stein, C. C. Almasan, S. H. Han, D. A. Gajewski, and M. B. Maple, "Two-Dimensional Localization and Superconductor-Insulator Transition in Strongly Underdoped Single Crystals of Y1-xPrxBa2Cu3O7-d (x <= 1)." Contact C. C. Almasan, Department of Physics, Kent State University, Kent, OH 44242; telephone (330) 672-2402; telefax (330) 672- 2959; e-mail calmasan@physics.kent.edu. 72.15.Rn; 74.20.Mn.
S. Li, J. C. Zhao, Q. Y. Hu, S. X. Dou, and W. Gao, "Lattice Distortion Measurement of (Bi,Pb)2Sr2Ca2Cu3O10+x Oxide in Silver Clad Wires with Mechanical Deformation." To be published in Physica C (in press). Contact W. Gao, Department of Chemical Materials Engineering, University of Auckland, Auckland, NEW ZEALAND; telefax +64 9 373 7463; e-mail w.gao@auckland.ac.nz.
M. F. Limonov, A. I. Rykov, S. Tajima and A. Yamanaka, "Raman Scattering Study on Fully Oxygenated YBa2Cu3O7 Single Crystals: X-Y Anisotropy in the Superconductivity-Induced Effects." To be published in Phys. Rev. Lett. 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. 74.25.Gz; 74.25.Kc; 74.72.Bk
M. Y. Lin, J. T. Huang, H.-C.I. Kao, and C. M. Wang, "Preparation, Structure, and Peritectic Transition of RBa1.5Sr0.5Cu3Oy (R=La, Nd, Sm, Eu, Gd, Dy, Ho, and Y) Superconductors." To be published in Mater. Res. Bull. Department of Chemistry, Tamkang University, Tamsui 25137, Taiwan, REPUBLIC OF CHINA; C. M. Wang's e-mail wangcm@mail.tku.edu.tw. Key words: oxides, superconductors, crystal structure, thermodynamic properties.
E. Maiser, P. Fournier, J.-L. Peng, F. M. Araujo-Moreira, T. Venkatesan, R. L. Greene, and G. Czjzek, "Pulsed-Laser Deposition of Pr2-xCexCuO4-y Thin Films and the Effect of High-Temperature Post-Annealing." To be published in Physica C. Forschungszentrum Karlsruhe, Institut fuer Nukleare Festkoerperphysik, P.O. Box 3640, D-76021 Karlsruhe, GERMANY; telephone +49 7247 82 3985; telefax +49 7247 82 4624; e-mail maiser@infp.fzk.de. Key words: electron-doped superconductor, thin films, phase diagram.
C. Marechal, E. Lacaze, W. Seiler, and J. Perriere, "Growth Mechanisms of Laser Deposited BiSrCaCuO Films on MgO Substrates." To be published in Physica C (in press). Faculte des Sciences, Laboratoire de Physique de la Matiere Condensee, Universite de Picardie-Jules Verne, 33 rue Saint Leu, F-80039 Amiens Cedex, FRANCE; telephone +33 3 2282 7804; telefax +33 3 2282 78 91; e-mail marechal@pmc.u-picardie.fr. Key words: BiSrCaCuO, laser ablation, thin film, epitaxial orientation, growth mode.
S. Marinel, J. Provost, and G. Desgardin, "The Crystal Growth Anisotropy of YBa2Cu3O7-d Fabricated by the MTG Method in a Microwave Cavity." To be published in Physica C (in press). Laboratoire CRISMAT, UMR CNRS 6508, ISMRA, Boulevard Marechal Juin, F-14050 Caen Cedex, FRANCE; e-mail marinel@crismat.ismra.fr. 61.50.Jr; 81.10.Fq; 81.10.Hs.
Y. Nakamura, K. Tachibana, S. Kato, T. Ban, S. I. Yoo, and H. Fujimoto, "Phase Relation in Y211-Y123-Ag System and Morphology of Silver in Y123 Crystal." To be published in Physica C (in press). Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185, JAPAN; telephone +81 425 73 7297; telefax +81 425 73 7297; e-mail yuichi_n@rtri.or.jp. Key words: melt processing, YBCO, Ag addition, phase relation, microstructure.
M. R. Norman and H. Ding, "Collective Modes and the Superconducting State Spectral Function of Bi2212." Submitted to Phys. Rev. B. Materials Science Division-223, Argonne National Laboratory, Argonne, IL 60439; telephone (630) 252-3518; telefax (630) 252-7777; e-mail norman@thio.msd.anl.gov; preprint also available at cond- mat@xxx.lanl.gov (#9712116). 71.25.Hc; 74.25.Jb; 74.72.Hs; 79.60.Bm.
Akihiro Odagawa, Masahiro Sakai, Hideaki Adachi, and Kentaro Setsune, "Characteristics of Intrinsic Josephson Junctions in a Thin Stack on Bi- 2223 Thin Films." To be published in Jpn. J. Appl. Phys. Central Research Laboratories, Matsushita Electric Industrial Co., Ltd., 3-4 Hikaridai, Seika, Soraku, Kyoto 619-02, JAPAN; telephone +81 774 98 2514; telefax +81 774 98 2585; e-mail odagawa@crl.mei.co.jp. Key words: high-Tc superconductor, intrinsic Josephson junction, (Bi,Pb)2Sr2Ca2Cu3O10+x , thin films, superconductive gap, current- voltage characteristics, small number of stacked junctions.
Akihiro Odagawa, Masahiro Sakai, Hideaki Adachi, and Kentaro Setsune, "Microwave Response of Intrinsic Josephson Junctions on Bi-2223." To be published in the Proc. of the 10th Int. Symp. on Supercond. (ISS'97), Gifu, Japan, Oct. 27-30, 1997. Central Research Laboratories, Matsushita Electric Industrial Co., Ltd., 3-4 Hikaridai, Seika, Soraku, Kyoto 619-02, JAPAN; telephone +81 774 98 2514; telefax +81 774 98 2585; e-mail odagawa@crl.mei.co.jp. Key words: intrinsic junction, Bi-2223 thin films, superconductive gap, microwave response.
Enrick Olive and Ernst Helmut Brandt, "On Point Defects in the Flux-Line Lattice of Superconductors." Submitted to Phys. Rev. B. Max Planck Institut fuer Metallforschung, POB 800665, D-70506 Stuttgart, GERMANY; Ernst Helmut Brandt's telephone +49 711 689 1823; telefax +49 711 689 1010; e-mail ehb@physix.mpi-stuttgart.mpg.de. 74.60.Ge; 61.72.Ji.
David Pines, "The Spin Fluctuation Model for High Temperature Superconductivity: Progress and Prospects." Submitted to the Proc. of the NATO Adv. Study Inst. on the Gap Symmetry and Fluctuations in High- Tc Supercond., Corsica, France, Sept. 1-12, 1997. Department of Physics, Loomis Laboratory of Physics, University of Illinois at Urbana- Champaign, 1110 West Green Street, Urbana, IL 61801-3080; telephone (217) 333-0115; telefax (217) 244-7559; e-mail d-pines@uiuc.edu.
P. Quemerais and S. Fratini, "Polaron Dissociation at the Insulator-to- Metal Transition." To be published in Mod. Phys. Lett. B. Contact S. Fratini, Laboratoire d'Etudes des Proprietes Electroniques des Solides (LEPES/CNRS), BP166, F-38042 Grenoble Cedex 9, FRANCE; e-mail fratini@lepes.polycnrs-gre.fr; preprint also available at cond- mat@xxx.lanl.gov (#9709182).
D. Rainer, H. Burkhardt, M. Fogelstroem, and J. A. Sauls, "Andreev Bound States, Surfaces and Subdominant Pairing in High Tc Superconductors." To be published in the Proc. of the Conf. on Spectroscopies in Novel Supercond. (SNS'97), Cape Cod, Mass., Sept. 14-18, 1997. Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth, GERMANY; J. A. Sauls' e-mail at Northwestern University in Evanston, IL is sauls@snowmass.phys.nwu.edu.; preprint also available at cond- mat@xxx.lanl.gov (#9712234).
G. Ravikumar, T. V. Chandrasekhar Rao, P. K. Mishra, V. C. Sahni, S. S. Banerjee, A. K. Grover, S. Ramakrishnan, S. Bhattacharya, M. J. Higgins, E. Yamamoto, Y. Haga, M. Hedo, Y. Inada, and Y. Onuki, "A Novel Technique to Measure Magnetization Hysteresis Curves in the Peak Effect Regime of Superconductors." Submitted to Physica C. Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085, INDIA.
E. B. Rudnyi, V. V. Kuzmenko, and G. F. Voronin, "Simultaneous Assessment of the YBa2Cu3O6+z Thermodynamics Under the Linear Error Model." Submitted to J. Phys. Chem. Ref. Data. Department of Chemistry, Moscow State University, 119899 Moscow, RUSSIA; telephone +7 095-939 5452; telefax +7 095-932 8846 or -939 1205; e-mail rudnyi@comp.chem.msu.su; Web site http://www.chem.msu.su/~rudnyi/welcome.html. Key words: high- temperature superconductor, chemical thermodynamics, Gibbs energy, enthalpy of formation, entropy, heat capacity, lattice model, visualizing quality of the fit, maximum likelihood, mixed model, variance component.
H. Sato, H. Yamamoto, and M. Naito, "Growth of La2-xSrxCuO4 and La2CuO4+d Thin Films by Reactive Coevaporation." To be published in the Proc. of the 1997 Fall Meeting of the Mater. Res. Soc., Boston, Mass., Dec. 1-5, 1997. NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-01, JAPAN; telephone +81 462 40 3532; telefax +81 462 70 2364; e-mail hisashi@will.brl.ntt.co.jp.
Stefan Scheidl and Valerii M. Vinokur, "Dynamic Melting and Decoupling of the Vortex Lattice in Layered Superconductors." Submitted to Phys. Rev. B. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov; preprint also available at cond- mat@xxx.lanl.gov (#9712271). 74.25.Dw; 74.40.+k; 74.60.Ge.
F. Schmidl, S. Linzen, S. Wunderlich, and P. Seidel, "High-Tc dc-SQUIDs on Silicon Bicrystal Substrates Operating at 77 K." Submitted to Appl. Phys. Lett. Institut fuer Festkoerperphysik, Friedrich-Schiller- Universitaet Jena, Lessingstrasse 8, D-07743 Jena, GERMANY; P. Seidel's telephone +49 3641 947410; telefax +49 3641 947412; e-mail seidel@ifk.uni-jena.de. 85.25.Dq; 74.50.+r; 68.55.-a.
S. V. Shulga, S.-L. Drechsler, G. Fuchs, K.-H. Mueller, K. Winzer, M. Heinecke, and K. Krug, "Upper Critical Field Peculiarities of Superconducting YNi2B2C and LuNi2B2C." To be published in Phys. Rev. Lett. Contact S.-L. Drechsler, Institut fuer Feskoerper- und Werkstofforschung Dresden e.V., Postfach 270016, D-01171 Dresden, GERMANY; e-mail drechsler@ifw-dresden.de; preprint also available at cond-mat@xxx.lanl.gov (#9712174). 74.60.Ec; 74.70.Ad; 74.20.-z; 74.72.Ny.
D. E. Steinhauer, C. P. Vlahacos, S. K. Dutta, B. J. Feenstra, F. C. Wellstood, and Steven M. Anlage, "Quantitative Imaging of Sheet Resistance with a Scanning Near-Field Microwave Microscope." To be published in Appl. Phys. Lett. Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742- 4111; telephone (301) 405-7670; telefax (301) 405-3779; e-mail steinhau@squid.umd.edu; Web site http://www.csr.umd.edu/research/hifreq/micr_microscopy.html; preprint also available at cond-mat@xxx.lanl.gov (#9712171).
T. Strohm, D. Munzar, and M. Cardona, "Comment on 'Screening of the B_[1g] Raman Response in d-Wave Superconductors.'" Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY.
S. Uma, W. Schnelle, E. Gmelin, G. Rangarajan, S. Skanthakumar, J. W. Lynn, R. Walter, T. Lorenz, B. Buechner, E. Walker, and A. Erb, "Magnetic Ordering in Single Crystals of PrBa2Cu3O7-d." To be published in J. Phys. Cond. Mat. Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; telephone +49 711 689 1364; telefax +49 711 689 1010; e-mail uma@tilux.mpi-stuttgart.mpg.de.
S. O. Valenzuela, H. Ferrari, V. Bekeris, M. C. Marconi, J. Guimpel, and F. de la Cruz, "Nonconventional Short-Time dc Magnetometer for Superconducting Films." To be published in Rev. Sci. Instrum. (in press). Laboratorio de Bajas Temperaturas, F.C.E. y N. Universidad Nacional de Buenos Aires, ARGENTINA.
N. Vandewalle, E. Pirard, R. Cloots, and M. Ausloos, "The Non-Trivial Dispersion of Y2BaCuO5 Particles Trapped in the YBa2Cu3O7-x Crystal Matrix." To be published in Phil. Mag. Lett. SUPRAS, Institute of Physics B5, University of Liege, B-4000 Liege, BELGIUM; e-mail vandewal@gw.unipc.ulg.ac.be. 07.05.Pj; 74.72.Bk; 74.72.Lw.
Roy Weinstein, Ravi Sawh, Yanru Ren, and Drew Parks, "The Role of Uranium, with and without Irradiation, in the Achievement of Jc ~ 300,000 A/cm^2 at 77 K in Large Grain Melt Textured Y123." Presented at the Int. Workshop on the Proc. and Appl. of Supercond. (RE)BCO Large Grain Materials, Cambridge, U.K., July 7-9, 1997. Beam Particle Dynamics Group and TCSUH, University of Houston, Houston, TX 77204- 5506. Key words: pinning centers, high Jc in Y123, fission damage in HTS, new chemical pinning center, trapped field magnet, strong pinning.
X. S. Wu, S. S. Jiang, W. M. Chen, Z. S. Lin, X. Jin, Z. Q. Mao, G. J. Xu, and Y. H. Zhang, "Microstrains in La1.85Sr0.15Cu1-yMyO4 (M=Zn,Ni,Mg) Cuprates with y <= 0.30." To be published in Physica C (in press). National Laboratory of Solid State Microstructures, Institute of Solid State Physics, and Center for Advanced Studies in Science and Technology of Microstructures, Nanjing University, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA. Key words: La1.85Sr0.15Cu1-yMyO4 (M=Zn,Ni,Mg) cuprates, room-temperature resistivity, x-ray diffraction, broadness of reflection, average lattice microstrain.
Y. G. Zhao, Z. W. Dong, M. Rajeswari, R. P. Sharma, and T. Venkatesan, "Growth of Single-Phase PrBa0.7Sr1.3Cu3O7 Thin Films and the Role of Lattice Strain on the Transport Properties." To be published in Appl. Phys. Lett. Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742; e-mail yzhao@squid.umd.edu.
Y. T. Zhu, E. J. Peterson, P. S. Baldonado, J. Y. Coulter, D. E. Peterson, and F. M. Mueller, "Synthesis and Crystal Chemistry of the New Compounds GdBa4Cu3O8.5+d and DyBa4Cu3O8.5+d." Materials Science and Technology Division, Mail Stop G755, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 667-4029; telefax (505) 667-2264; e- mail yzhu@lanl.gov. Key words: Gd143, Dy143, Rietveld refinement, crystal structure, space group, cuprate.
Igor Zutic and Oriol T. Valls, "Computation of the Nonlinear Magnetic Response of a Three Dimensional Anisotropic Superconductor." To be published in J. Appl. Phys. School of Physics and Astronomy and Minnesota Supercomputer Institute, 116 Church Street S.E., University of Minnesota, Minneapolis, MN 55455-0149; telephone (612) 624-7375; telefax (612) 624-4578; e-mail izutic@physics.spa.umn.edu; Web site http://www.member.com/igor; preprint also available at cond- mat@xxx.lanl.gov (#9712210).
COMING EVENTS (An * indicates a previously listed event.)
Feb. 23 - 27, 1998: UCLA Information Systems and Technical Management Short Course -- Advanced Long Life Cryocoolers, UCLA, Los Angeles, Calif. This course provides a thorough introduction to cryocoolers. Regenerative cryocoolers emphasized are Stirling, Vuilleumier, Gifford- McMahon, and pulse tube. Recuperative systems include the Joule- Thomson, Brayton, and Claude cycle. Instruction focuses on small- and intermediate-capacity cryocoolers designed for infrared detectors, electronic devices, superconducting sensors, superconducting magnets, and cryopumps. Two site visits are included (to a UCLA Cryogenic Lab and to Jet Propulsion Lab in Pasadena). For further information, contact UCLA Extension, 10995 Le Conte Avenue, Los Angeles, CA 90024- 2883; telephone (310) 825-3344; telefax (310) 206-2815.
*April 19 - 24, 1998: The Seventh Conference on Frontiers of Electron Microscopy in Materials Science (FEMMS98), Kloster Irsee, Irsee, Germany. Purpose of this meeting is to establish the current state of the art of quantification of all relevant techniques used in electron microscopy including XEDS, EELS, Z-contrast, HREM, conventional TEM, CBED, and in-situ. Topical area: quantitative methods in electron microscopy. Number of participants limited to 100 (30 invited speakers, 20 invited session chairs, and 50 participants). Abstract deadline, January 15, 1998; registration deadline, February 16, 1998. For information, contact Kloster Irsee, Schwaebisches Tagungs- und Bildungszentrum, Klosterring 4, 87660 Irsee, Germany; telephone +49 8341 906-00; telefax +49 8341 742-78; Web site http://femms98.llnl.gov.
April 29 - May 2, 1998: 15th Annual International Convention: The High Speed Ground Transportation Association, Chicago Westin Hotel, Chicago, Illinois. The three-day program will include technological updates; environmental issues; federal, state, and local government policy discussions; international project developments; project management tools and techniques; state and regional updates; and financing alternatives. Contact HSGTA, 1010 Massachusetts Avenue, Suite 110, Washington, DC 20001; telephone (202) 789-8107; telefax (202) 789-8109.
May 10 - 13, 1998: International Cryogenic Materials Conference (ICMC'98) -- Topical Conference on Loss and Stability in High-Tc and Low-Tc Superconductors, University of Twente, Enschede, The Netherlands. Aim is to bring together experts working on the electrodynamics of technical superconductors. In particular ac loss and stability issues in high-Tc and low-Tc conductors are addressed. Contributions for both materials are requested for better understanding of ac loss, current distribution, and stability. Key topics are: ac losses in tapes, wires, cables, and coated conductors; effectiveness of filament decoupling layers, twisting, and mixed-alloy matrices; strand coating and sheet barriers to decouple cable stages (ITER, SMES, and other pulsed magnets); cores in Rutherford cables to decouple crossing strands (accelerator magnets); geometrical effects -- multilayers of tapes in high-Tc cables, non-uniform dB/dt, non-equal current sharing; and physical and numerical modelling of ac losses and stability -- similarities and differences between high-Tc and low-Tc conductors, multiple time constants in multistage cables, and continuum versus network models. Abstract deadline, January 16, 1998; preregistration deadline, March 1, 1998. For information, contact Arend Nijhuis, Conference Secretary, P.O. Box 217, NL 7500 AE Enschede, The Netherlands; telephone +31 53 489 3841; telefax +31 53 489 1099; e-mail icmc98@tn.utwente.nl.
July 26 - Aug. 8, 1998: NATO Advanced Study Institute -- Physics and Materials Sciences of the Vortex States, Flux Pinning, and Dynamics, Kusadasi, Turkey. Topics include statistical mechanical vortex lines, phase transitions in vortex ensemble, critical currents and microstructure, magnetic flux penetration and vortex dynamics in HTSC films, pinning mechanisms in high-temperature superconductors, magneto- optical study of flux penetration, statistics and dynamics of flux-line lattice in realistic geometries, vortex statics and dissipation-related properties in layered HTSC, practical issues of flux pinning and vortex dynamics for HTS materials, static and dynamic vortex states, Josephson vortex dynamics in layered structures, relevance of flux pinning and dynamics to engineering applications of high-temperature superconductors, and flux distribution instabilities in a current- carrying state of type-II superconductors. Application deadline, March 1, 1998. For information, contact Ram Kossowsky, ETI, 6327 Burchfield Avenue, Pittsburgh, PA 15217; telephone (412) 421-4408; telefax (412) 421-4342; e-mail ramkoss@mindspring.com.
Sept. 25 - Oct. 2, 1998: First Crete Euroconference on Anomalous Complex Superconductors (ACS-I), Heraklion, Greece. Objective is to initiate a simultaneous comparative study of characteristic anomalies of high-Tc superconductors and analogous anomalies in other "complex'' superconductors like heavy fermions, organics, fullerides, borocarbides, ruthenates, etc. In-depth simultaneous comparative analysis of all manifestations of complex behavior in the various materials will be pursued in order to "distinguish relevant from irrelevant aspects for high-Tc superconductors and to obtain some systematic theoretical understanding of the mechanisms through which this complex behavior influences Tc." For further information, contact Georgios Varelogiannis, IESL-FORTH, P.O. Box 1527, 71110 Heraklion Crete, Greece; telephone +30 81 391565; telefax +30 81 391569; e-mail varelogi@iesl.forth.gr.
FIG. 1. Quantitative sheet resistance image (bottom) determined from measurements of the frequency shift and quality factor (top) acquired using a scanning near-field microwave microscope at 7.5 GHz [see preprint by D. E. Steinhauer et al. (Maryland)]. The sample is a variable-thickness YBCO thin film on a sapphire wafer, where the film is thickest at the center. A scanning probe with a 500 micrometers diameter center conductor was used at a height of 50 micrometers above the sample. The tick marks are 1 cm apart, and the arrows point to small semi-circular regions where clips held the wafer and blocked YBCO deposition.
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.
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. E-mail: MITRA@AMESLAB.GOV or MITRA@IASTATE.EDU.
Project Director/Editor: Sreeparna Mitra Science Editor: John R. Clem High-Tc Update, Vol. 12, #2, January 15, 1998.