YBa2Cu3O7-d
The growth of RBa2Cu3O7-d (R-123, R = rare earth, especially R = Y, Nd, and Sm) crystals has been studied in detail by Th. Wolf (Karlsruhe). The author shows that the anisotropic growth velocities of both crystals and melt-textured samples can be understood using the model of supersaturation. In this model, the melt viscosity, stirring the melt, and addition of solid phase to the melt all influence the growth rate of R-123. While the growth rate of most faces could be varied by a factor of 1000 up to about 2 mm/h, the growth rate of the (001) face was found to be constant at 4 micrometers/h.
The crystal-growth-rate anisotropy of YBa2Cu3O7-d (Y-123) using a modified pulling method has been investigated by Y. Namikawa and Y. Shiohara (SRL-ISTEC) using Y-123 single-crystal seeds. The growth rate (R_[ch]) of {001} faces on the side of a crystal grown along a <100> direction was found to be higher than the growth rate (R_[ah]) of {100} faces on the side, with R_[ch]/R_[ah] = 1.3. This growth-rate anisotropy is attributed to the low supersaturation obtained in the modified pulling method. The crystal-growth rate was found to be proportional to the square of the solute supersaturation. Several spiral patterns were observed on (001) faces, but none were found on (100) faces.
A new scheme for preparing bicrystals with well-defined planar interfaces useful for the investigation of the electrical behavior of grain boundaries in YBa2Cu3O7-d (Y-123) has been developed by V. R. Todt (Argonne) et al. The bicrystal misorientation was controlled by dual seeding using Nd1+xBa2-xCu3O7-d single crystals. The grain-boundary plane orientation was found to be influenced by the positioning of the seeds and by control of the temperature gradient. In a series of [001]-tilt boundaries, a difference in critical current density Jc(77K,0T) of nearly two orders of magnitude was found between samples with low (<10 degrees) and high (>20 degrees) misorientation angles.
Bulk melt-textured Y-123 samples in the shape of disks have been developed by G. Fuchs et al. (Dresden) for use as trapped-field magnets. The trapped field in single grains with a diameter of 24 mm reached maximum values up to 0.56 T at 77 K and 5.5 T at 30 K. Degradation of the trapped field, arising from magnetic stress-induced damage, was observed in samples after activation at 20 K in a high applied magnetic field.
As reported by J. Axnaes et al. (Royal Institute of Technology, Stockholm), the out-of-plane magnetoconductivity Delta-sigma_c (B||I||c axis) of two YBa2Cu3O7-d single crystals has been measured in magnetic fields up to 12 T at temperatures ranging from Tc + 3 K to Tc + 40 K. A change of sign, from negative Delta-sigma_c near Tc to positive values at higher temperatures, was observed in a metallic sample for which drho_c/dT > 0. The results can be described using recent fluctuation theories with parameters [xi_[ab](0) = 12 Angstroms and 14 Angstroms, and xi_c(0) = 1.8 Angstroms and 2.4 Angstroms for samples A and B, respectively] in good agreement with other studies.
Polarized reflection measurements on the (001) plane of various single-domain crystals of Y1-zCazBa2Cu3Ox with different Ca and O contents, z and x, have been carried out by K. Widder et al. (Karlsruhe). Using the in-plane anisotropy of the optical properties, the authors separated the contributions of the CuO2 layers and the CuO chains to the electronic transport properties. With increasing Ca doping, the authors found that the additional carriers introduced by Ca doping appear only in the CuO2 layers, while the doping of the chains was even reduced because of an increase of oxygen vacancies for samples with x close to seven. The superconducting transition temperature Tc was found to have a parabolic dependence upon the free-carrier concentration in the CuO2 layers, with an optimum Tc = 92 K at z = 0 and x = 6.93.
The effects upon transport coefficients of guided motion of vortices by twin planes are reported in two preprints listed in this issue. V. N. Morgoon (Lorena, Sao Paulo, and Kharkov State) et al. report observations of guided vortex motion and a Hall effect that is an even function of the magnetic field in YBa2Cu3O7-d single crystals containing a unidirectional twin array. H. Ghamlouch and M. Aubin (Sherbrooke) also observed this effect in YBa2Cu3O7-d and, in addition, found that guided vortex motion gives rise to a contribution to the Seebeck coefficient consisting of the Nernst coefficient multiplied by the Hall angle.
A preprint by H. Ghamlouch and M. Aubin (Sherbrooke) reports the observation of vortex-lattice melting in a detwinned YBa2Cu3O7-d single crystal using a Seebeck-effect measurement. In such experiments, the Seebeck voltage Delta-V along the length of the sample is measured as a function of the temperature difference Delta-T from one end to the other. The Seebeck coefficient S is defined as the ratio Delta-V/Delta-T in the limit Delta-T --> 0. Although the measurements do not employ a transport current, the temperature dependence of the Seebeck coefficient is expected to follow closely that of the resistivity rho via the relation S = (rho/rho_n)S_n, where the subscript n denotes normal-state values. Indeed, for temperature gradients applied along the b direction, the behavior of S vs. T in various magnetic fields H is strikingly similar to previously reported plots of rho vs. T in untwinned single crystals of YBa2Cu3O7-d, with a sharp rise and knee at the melting temperature T_m followed by a smooth rise into the normal state. The sharp rise, however, is not as sharp as for the resistivity because of the temperature gradient applied in the Seebeck experiments. The Seebeck signal was too small to measure along the a direction. The b-axis data were used to obtain a melting curve that can be fit by a theory of G. Blatter and B. I. Ivlev [Phys. Rev. B 50, 10272 (1994)] taking into account both thermal and quantum fluctuations.
Using neutron spectroscopy, A. T. Boothroyd (Oxford) et al. have measured the relaxation behavior of the 0.5 meV ground-state crystal-field transition of Ho^[3+] in Ho0.1Y0.9Ba2Cu3O7-d (Tc = 94 K). The authors studied the intrinsic linewidth Gamma and peak position over the temperature range 1.5-160 K. The data show an anomaly at ~115 K consistent with the formation of a superconducting energy gap. The authors extrapolate the normal-state linewidth Gamma_n to lower temperatures and hence evaluate the reduced relaxation rate Gamma/Gamma_n. Well below Tc, both Gamma/Gamma_n and the peak position show a significant temperature variation characteristic of a high degree of gap anisotropy.
Bi Cuprates
As reported by J. P. Singh (Argonne), Ag-sheathed tapes of Bi2Sr2Ca2Cu3O10+d (Bi-2223 or BSCCO) and Bi-2223/Ag superconducting cores have been fabricated by a powder-in-tube technique and subjected to thermomechanical cycles that resulted in improved grain alignment and increased critical current density Jc. Addition of Ag particles to the BSCCO core increased the resistance to crack propagation, giving rise to increased strain tolerance of the superconducting tapes. For BSCCO/Ag composite tapes, approximately 90% of the initial Jc was retained at an applied strain of 1.2%, whereas the monolithic tapes retained only 40%.
Bi-2223 superconducting tapes have been prepared by Y. Tanaka (NRIM) et al. via the powder-in-tube technique using Ag-10 at%Cu alloy sheaths with and without a small amount of doping elements of Ti, Zr, or Hf, and repetition of sintering and cold pressing. The doped samples showed a critical current density of Jc(4.2K,14T) = 5-9 x 10^4 A/cm^2. Amorphous, disk-like regions, less than 5 nm in thickness parallel to the (001) plane, were found to be incorporated in the Bi-2223 lattice only for the doped samples. The authors suggest that these amorphous regions are responsible for the enhanced critical currents.
A preprint by M. Houssa et al. (Liege) reports the determination of the superconducting fluctuation contribution kappa_[fl] from measurements of the thermal conductivity of a Bi2Sr1.8Ca1.2Cu2O8+d (Bi-2212) polycrystal. A crossover from 2D to 3D behavior theoretically predicted by A. A. Varlamov and D. V. Livanov [Sov. Phys. JETP 71, 325 (1990)] was observed. The crossover temperature and the amplitude of the fluctuation contribution lead to realistic values for the interlayer coupling energy and the transport relaxation time near Tc.
As reported by N. L. Wang et al. (Darmstadt), the authors have obtained underdoped Bi2Sr2CaCu2O8+d (Bi-2212) single crystals by using two different methods: (a) growing Y-doped crystals and (b) removing oxygen from crystals by vacuum annealing. The authors find that there are strong differences in the in-plane transport properties between these two crystals. The analysis indicates that the disorder introduced by vacuum annealing is much higher than that introduced by Y doping, as long as the crystals have the same Tc.
Polycrystalline samples of (Bi,Pb)Sr2(Y,Ca)Cu2O7-z [(Bi,Pb)-1212] have been prepared by H. Frank (RWTH-Aachen) et al. to study the influence of a missing BiO layer and to compare with the properties of Bi-2212 and (Bi,Pb)-2223. The authors' analysis showed a high percentage (~~80%) of the (Bi,Pb)-1212 phase in a sample with zero-resistance Tc = 92 K. The temperature dependence of Jc and the normalized relaxation rate are similar to those of Bi-2212 and (Bi,Pb)-2223, suggesting a similar anisotropy for all three compounds.
A number of Bi2Sr2-xLaxCuOy (La-doped Bi-2201) crystals with different doping levels have been grown and characterized by N. L. Wang et al. (Darmstadt). The anisotropic resistivity, measured by a generalization of the Montgomery method, was found to change in a systematic way. The analysis indicates that for all the samples the in-plane transport is on the metallic side of the Ioffe-Regel criterion, but the out-of-plane transport is deeply on the insulating side of the Mott limit. The temperature dependence of the c-axis resistivity rho_c(T) can be well understood from the incoherent hopping model proposed by Levin and co-workers.
Tl Cuprates
The effects of carbon on TlBa2Ca2Cu3O9 (Tl-1223) phase formation in the TlF-Ba2Ca2Cu3Oz system have been investigated by Y. S. Sung et al. (Argonne) by varying the carbon content in Ba2Ca2Cu3Oz precursor powders, which were mixed with TlF and reacted to form the superconducting phase. The authors found that carbon induced Tl2Ba2Ca2Cu3O10 (Tl-2223) formation, resulting in superlattices formed by c-axis intergrowths between Tl-1223 and Tl-2223. The superlattices were highly regular and uniform throughout the samples.
The thermal conductivity of Tl2Ba2CuO6+d (Tl-2201) crystals has been studied by F. Yu (Illinois-Urbana) et al. as a function of temperature and magnetic field. Near 0.6 Tc, the authors observed a thermal conductivity peak, which is greatly reduced in the presence of a magnetic field along the c axis. The suppression of the peak at relatively low fields (H <= 8 T << H_[c2]) enabled the authors to separate the electronic and phononic contributions. A model based on Andreev scattering of quasiparticles by vortex screening currents is shown to be consistent with the results.
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The observation of an increase in the superconducting transition temperature Tc of up to 7 K in phase-separating La2CuO4+d upon careful annealing in a narrow temperature range of 185 K to 210 K has been reported, but no related change in the microscopic structure has been reported until recently. A preprint by P. Wochner (Brookhaven) et al. now examines the implications for the superconducting properties of this structural phase transition, which involves a periodic one-dimensional modulation of the in-plane order. Microscopic modeling of new high-resolution neutron-scattering data leads to a picture where the excess oxygen, and therefore also the doped holes, order in stripes along the a direction in addition to staging along the c direction (which is present in both a-modulated and unmodulated phases). The authors' results provide an explanation for the annealing-induced Tc increase, which was confirmed by susceptibility measurements on the same sample to be as large as 2.5 K. The results also support the suggestion that spatial modulation of charge and spin density are related to superconductivity in the cuprates.
Systematic neutron-scattering studies have been performed by K. Yamada (Tohoku) et al. on identically treated float-zone-grown single crystals of La2-xSrxCuO4 over a wide doping range to study the spatially modulated dynamical spin correlations. The spatial modulation was found to first appear for x beyond the critical doping x_c for the superconducting phase. For x > x_c, the incommensurability d increases with x, following a d = x relation, but deviates downward beyond x ~~ 0.12. The authors also found that Tc increases linearly with d up to the optimal doping level x_0 ~~ 0.15.
Other Materials
A preprint by N. Khare (NPL-New Delhi) et al. reports the observation of rf SQUID effects due to natural grain-boundary weak links in a bulk sample of YNi2B2C superconductor (Tc = 15.5 K) at 4.2 K, confirming that the superconducting grains are coupled at the grain boundaries through the Josephson effect.
The superconducting properties of La3Ni2B2N3-d (Tc = 12.25 K) have been studied by H. Michor (TU-Wien) by means of resistivity, magnetization, and heat-capacity measurements. The authors conclude that this material is a phonon-mediated weak- to medium-coupling BCS superconductor.
As reported by S. A. Carter et al. (Bell Labs), substantial hole doping has been achieved in the CuO2 chains of the ladder compound (La,Sr,Ca)14Cu24O41. The two-leg Cu2O3 ladders, however, remain undoped and magnetically inert because of a large spin gap. The authors find that the moments in the undoped chains interact weakly, and that every hole added creates a nonmagnetic CuO2 unit and decreases the resistivity. No superconductivity was observed.
A new type of lanthanide transition metal pnictide-oxide, Ln3Cu4P4O2 (Ln = La, Ce, and Nd), is reported by R. J. Cava (Bell Labs) et al. The crystal structure, made from Ln2O2 layers of the Pb2O2 type stacked with layers of Cu2P2 tetrahedra, indicates the existence of a homologous series of compounds with similar chemistry connecting the BiCuOSe and ThCr2Si2 structure types. The resistivity of Ln3Cu4P4O2 is metallic, but no superconductivity is observed above 2 K.
Thin Films
The vortex-solid phase boundary of YBa2Cu3O7-d (YBCO) thin films has been studied by L. Hou (Purdue) et al. as a function of d using magneto-transport measurements. From critical scaling analyses of E vs. J curves, the authors determined the vortex-glass phase boundaries H_g vs. T. The authors found experimental evidence for a dimensional crossover field H_0, separating three-dimensional from quasi-two-dimensional behavior, for films with d > 0.12 at a temperature T_0 ~~ Tc/2. When plotted as H_g(T)/H_0 vs. (1-T/Tc), all of the phase boundaries collapse onto a single universal curve. The authors conclude that the empirical equation H_g(T) = H_0[(1-T/Tc)/(1-T_0/Tc)]^n, where H_0 = 1.2phi_0/(s_[gamma])^2, s is the layer spacing, gamma is the anisotropy, n ~~ 3/2 for T > T_0, and n ~~ 3 for T < T_0, can be used to describe the vortex-glass boundary for any YBCO film and other disordered YBCO materials.
Nanovolt-level dc measurements on single-unit-cell films of YBa2Cu3O7-d have been carried out by J. M. Repaci (Maryland) et al. When only the low-sensitivity data are analyzed, they are consistent with the occurrence of a Kosterlitz-Thouless transition. At the lowest currents and voltages, however, the samples are found to be ohmic, indicating the presence of unbound vortices, at temperatures well below the nominal Kosterlitz-Thouless transition temperature, contrary to the theory.
A preprint by J.-Y. Lee et al. (KIST) reports a method for absolute measurements of the penetration depth lambda(T) of large-area YBa2Cu3O7-d films using a two-coil method. The YBCO film, placed on top of a 1 micrometer thick Pb film of the same size, is positioned in the gap between the drive and receive coil. The transition of the Pb film produces a step in the mutual inductance M(T) vs. T, and the absolute value of the YBCO's lambda(T) can be obtained from the resulting step height.
The effect of vortex pinning by surface roughness in YBa2Cu3O7-d thin films has been modeled by Ch. Jooss et al. (MPI-Stuttgart). The authors conclude that surface roughness typically contributes between 10% and 30% of the total Jc in high-quality epitaxial YBCO films.
Persistent photoinduced changes of intrinsic (critical temperature) and extrinsic (field-cooled magnetization and hysteresis-loop width) superconducting parameters of Tl2Ba2CaCu2O8+d (Tl-2212) thin films have been observed by H. Szymczak (Warsaw) et al. Relaxation back to the original state is very slow, of the order of days, at room temperature. The authors explain the data in terms of two different types of photosensitive pinning centers.
As reported by Z. F. Ren (SUNY-Buffalo) et al., epitaxial films of Tl2Ba2CuO6+d (Tl-2201) have been prepared on SrTiO3 by sputtering and post-deposition annealing. Although the annealed films typically exhibit transition temperatures of about 11 K, subsequent re-annealing to optimize the oxygen doping increases Tc to about 83 K. Analyses of the crystal structure of these films revealed that both the 11 K and 83 K films have a tetragonal crystal structure.
High-resolution electron-microscopy (HREM) studies of Bi2Sr2CaCu2O8+d (Bi-2212) thin films containing defects produced by 200 MeV [40]^Ca, 2640 MeV [197]^Au, and 1404 MeV [238]^U ion irradiation are reported by J. Wiesner (Delft and Darmstadt) et al. The HREM study, showing both longitudinal and transverse cross sections, clearly demonstrates that swift heavy ions produce well-defined latent columnar tracks consisting of totally amorphized material separated by a sharp transition from the surrounding crystalline material. Correlations of HREM and transport critical current (Jc) measurements showed that continuous columnar defects ([197]^Au and [238]^U) are more efficient pinning centers than scattered defect cascades ([40]^Ca).
Applications
As stressed in a preprint by D. Ponnusamy (TCSUH) et al., current leads made of ceramic superconductors promise to be one of the first applications of these materials. Their high critical temperature and low thermal conductivity make them suitable for current leads to low-Tc devices. The authors describe the fabrication and performance of current leads made of BSCCO rods and tubes.
The critical currents of superconducting silver and silver-alloy composite double pancake coils of Bi1.80Pb0.33Sr1.87Ca2.00Cu3.00O10+d [(Bi,Pb)-2223] have been measured by N. V. Vo et al. (Wollongong) at liquid-nitrogen temperature. A critical current density of ~1.25 x 10^4 A/cm^2 was obtained for a coil of [(Bi,Pb)-2223]/Ag composite tape of length ~2.2 m (~342 ampere-turns) fabricated using the wire-in-tube method. The authors report that the critical currents of coils made of tapes with a silver-alloy matrix (e.g., ~0.02%Mg) are higher than in those with a pure silver matrix.
Radio-frequency SQUID (superconducting quantum interference device) sensors have been fabricated by A. K. Gupta et al. (NPL-New Delhi) using natural grain-boundary weak links in high-Tc Bi2Sr2Ca2Cu3O10+d (Bi-2223) screen-printed thick films. The films have predominantly the high-Tc 2223 phase, are c-axis oriented with large grains (25-30 micrometers), and have a zero-resistance Tc = 104 K. The sensors show good voltage-flux (V-Phi) characteristics at 77 K. The authors have shown the potential of such rf SQUIDs for nondestructive detection of defects in steel plates.
The development of a high-Tc thick-film magnetometer based on measurements of the amplitude of the second-harmonic response of a superconducting Bi(Pb)-Sr-Ca-Cu-O screen-printed thick film is reported in a preprint by N. Khare et al. (NPL-New Delhi).
As reported by N. Khare (NPL-New Delhi), an rf SQUID has been fabricated from a (Hg,Tl)-1223 film with zero-resistance Tc = 123 K. SQUID behavior, arising from naturally present grain-boundary junctions, was observed up to 117.5 K.
Theory
The density of states (DOS) of quasiparticle excitations in the superconducting state of the high-Tc cuprates has been calculated by J. Bok and J. Bouvier (CNRS-Paris) using an anisotropic-gap model based on the van Hove scenario, in which the Fermi level lies close to singularities in the DOS. The authors obtain results in good agreement with tunneling I-V experiments using break junctions and vacuum scanning tunneling spectroscopy. The authors explain structure observed in the gap and also reproduce the observed asymmetry in the conductance and the dip in the DOS seen in photoemission.
Exact-diagonalization studies of the generalized 2D t-J Holstein model have been carried out by T. Sakai (Toulouse) et al. The results give evidence for stabilization of two-hole pairing by out-of-plane buckling vibrations of the in-plane oxygens in the high-Tc cuprates. On the other hand, in-plane breathing modes suppress the pairing.
A preprint by R. A. Klemm (Argonne) proposes two new geometries for Josephson-junction experiments between the edge of an orthorhombic, untwinned single-crystal high-Tc superconductor, assumed to have an order parameter of mixed s +- d_[x^2-y^2] symmetry, and a conventional, s-wave superconductor. The first geometry is a straight edge Josephson junction cut at an angle relative to the a-axis edge of a high-Tc crystal. The second is a disk cut from a high-Tc single crystal, with a Josephson junction formed on the edge with an angular width Delta-Phi.
Two preprints by Y. N. Obukhov and F. E. Schunck (Koeln) present cylindrically symmetric numerical solutions of the Ginzburg-Landau equations for type-II superconductors. The authors consider solutions that are different from the usual singly quantized Abrikosov vortices, and they call these solutions type-B and flux-tube solutions. The authors conclude that Abrikosov vortices are energetically favorable only in the field range between the lower critical field H_[c1] and the thermodynamic critical field H_c, and that the cylindrically symmetric flux-tube solutions are energetically favored between H_c and the upper critical field H_[c2].
The Ginzburg-Landau equations for a superconductor with both s- and d-wave coupling in the presence of nonmagnetic impurities have been derived microscopically from the Gor'kov equations by W. Xu (Nanjing and TCSUH) et al. The authors find that as the concentration of nonmagnetic impurities increases, the system changes from a d-wave-pairing state to an s-wave state, with a mixed s + id state appearing in between.
A preprint by D. Ertas and D. R. Nelson (Harvard) discusses the onset of irreversibility and entanglement of vortex lines in high-Tc superconductors due to point disorder and thermal fluctuations using a simplified cage model. A combination of Flory arguments, known results from directed polymers in random media, and a Lindemann criterion are used to estimate the field and temperature dependence of irreversibility, mechanical entanglement, and thermal melting. The qualitative features of this dependence, including its nonmonotonic behavior when disorder is sufficiently strong, are in good agreement with recent experiments.
Cross-correlations in the magnetic-flux noise due to thermally activated movements of a pancake-vortex lattice in strongly anisotropic layered superconductors have been investigated theoretically by V. D. Ashkenazy (Bar-Ilan) et al. The authors show that below a crossover frequency, which depends on the sample thickness, vortices in layered superconductors behave as rigid rods, resulting in fully coherent motions of pancakes on opposite sides of the sample.
Antiferromagnetic spin-1/2 Heisenberg ladders, consisting of n_c chains (2 <= n_c <= 6), have been studied by M. Greven et al. (MIT) as a function of the inter- to intrachain coupling ratio J_[perp.]/J_[parallel] using Monte Carlo simulations. The results provide a good description of neutron-scattering measurements of the correlation length in the prototype S = 1/2 square-lattice Heisenberg antiferromagnet Sr2CuO2Cl2.
Using exact diagonalization techniques, C. A. Hayward (Toulouse) et al. have studied the magnetization of a Heisenberg spin ladder and found three distinct magnetic phases. The authors discuss their results in connection with experiments on the compound Cu2(C5H12N2)2Cl4 and deduce that this compound is well described by such a model with a ratio of chain to rung bond strengths J/J' of the order of 0.2, consistent with magnetic-susceptibility results.
Other Activities
Two preprints by A. Sanchez and C. Navau (Barcelona) present theoretical results for the magnetic levitation of type-II superconductors above a permanent magnet. One of these papers considers the levitation of a thin superconducting disk, and the other considers the levitation force, magnetic stiffness, and damping for a type-II superconducting cylinder above a cylindrical permanent magnet.
A preprint by V. V. Moshchalkov (Leuven) et al. reports that the paramagnetic Meissner effect (PME) can be explained by the persistence of the giant vortex state with fixed orbital quantum number L. The authors note that this state is formed during field cooling as the field passes through the third critical field H_[c3]. The authors present numerical solutions of the Ginzburg-Landau equations showing that compression of the flux trapped inside the giant-vortex state results in the PME. The authors note that the PME is suppressed and the normal diamagnetic response recovered when the applied field is increased.
A two-fluid critical-state model for describing the ac susceptibility of ceramic high-Tc superconductors is presented in a paper by O. F. Schilling (Santa Catarina) et al. The authors show that the model reproduces the experimentally observed ripple-field-amplitude and frequency dependencies of the ac susceptibility.
Overviews
Various experimental efforts to probe the symmetry of the order parameter in high-Tc superconductors are discussed in a review chapter by N. Khare (NPL-New Delhi). Included are penetration-depth measurements, nuclear-magnetic-resonance (NMR) studies, angle-resolved photoemission spectroscopy (ARPES), low-field magnetic-susceptibility measurements, phase-sensitive SQUID measurements, flux-imaging experiments, interference experiments, and Josephson tunneling experiments. The author presents a table listing various experiments and the order-parameter symmetry that best explains each experiment (55 refs.).
The status of applications of high-temperature superconductors (HTS) has been summarized in a paper by U. Balachandran and A. N. Iyer (Argonne). The authors discuss the properties of YBa2Cu3O7-d (YBCO) and Bi2Sr2Ca2Cu3O10+d (Bi-2223), HTS wire development, YBCO tapes produced on zirconia substrates aligned by ion-beam-assisted deposition (IBAD), prototype power transmission cables, magnets, transformers, motors, current leads, fault-current limiters, SQUIDs, and HTS filters for cellular telephone technology (43 refs.).
A brief review of the dynamic and thermodynamic experimental evidence supporting first-order melting of the vortex lattice in clean crystals of YBa2Cu3O7-d has been prepared by G. W. Crabtree et al. (Argonne). Resistivity measurements, SQUID magnetometry, and calorimetry all show evidence for a first-order transition in untwinned crystals (24 refs.).
Contributed by John R. Clem
Contents: Technology News begins on page 6; Preprints begin on page 7; Coming Events begin on page 14; and Resources are 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.
(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.
A team led by DuPont has announced a successful demonstration of a high-temperature superconducing magnet used in a chemical process application. In the demonstration, an HTS magnet separator was used to separate and remove mineral contaminants from kaolin (a white clay used extensively in paper processing). Comparison to the performance with a similar unit using a conventional electromagnet separator showed that the HTS separator enabled a higher throughput of the clay at higher magnetic field levels. The HTS magnet used was produced by Sumitomo Electric Industries, Ltd., and the kaolin slurries, prepared from commercial deposits, were provided by Aquafine, a leader in the sales of conventional magnetic separators. DuPont officials say that the demonstration opens the door for HTS magnet usage in other mineral-separation and chemical-processing applications, from catalysts and polymerization to environmental cleanup. For further information, contact Nancy Tidona, E. I. DuPont de Nemours & Company, Experimental Station, P.O. Box 80328, Wilmington, DE 19880-0328; telephone (302) 774-7447.
A new technology to monitor the current flow through high-temperature superconductors by imaging magnetic-field patterns was developed under a cooperative research and development agreement (CRADA) among Argonne, Phase Metrics (San Diego, CA), and the Institute of Solid State Physics (Moscow, Russia). The technology consists of an optical cryostat containing the sample mounted on top of a polarized light microscope, and an image processing system. The magneto-optical images are a suitable tool for the contactless, noninvasive quality control of superconducting products. The images of the field distribution reveal nonuniform superconducting characteristics like weak links and nonuniform pinning forces, whereas traditional probes reveal only the average response of the sample. The high resolution of the field maps allows specific defects like grain boundaries and precipitates to be studied. Researchers hope to use the information to help determine where and why current flow stops, and eventually improve superconducting materials' ability to carry current. The same qualities that make the system ideal for studying superconductors could also be applied to the development of new magnetic materials, such as giant magnetoresistance and magnetic multilayer systems. For further information, contact Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439.
With previous successful field tests at GTE (California), Cellcom (Wisconsin), and Kansas Cellular, the Conductus front-end receiver subsystem consisting of a superconducting bandpass filter was most recently tested at Triad Cellular sites in the Texas Panhandle, where the system's increased uplink sensitivity provided voice quality and coverage improvements in the cell-site service area. Triad is discussing the possibility of deploying several Conductus systems for extended evaluation this fall. Conductus, in a planned evaluation period in the near future, intends to monitor several key parameters such as perceived improvements in cellular phone quality evaluated through a poll of local subscribers who routinely use upgraded sections of the networks, and hopes to put a "dollars per dB" figure of merit on technical benefits. For further information, contact Stephen M. Garrison, Product Marketing Manager, Conductus, Inc., 969 West Maude Ave., Sunnyvale, CA 94086; telephone (408) 523-9430; telefax (408) 523-9999.
Contributed by Sreeparna Mitra
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.
Liliana Arrachea, A. A. Aligia, and E. Gagliano, "Study of the Metal-Insulator Transition and Superconducting Correlations of a Generalized Hubbard Model." To be published in Physica C (in press). Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, 8400 Bariloche, ARGENTINA.
V. D. Ashkenazy, G. Jung, and B. Ya. Shapiro, "Cross-Correlation of Thermal Flux Noise in Layered Superconductors." Submitted to Phys. Rev. B. Department of Physics, Ben Gurion University of the Negev, 84105 Beer-Sheva, ISRAEL. 74.40.+k; 74.60.Ge; 74.80.Dm.
Marcel Aubin, Hassan Ghamlouch, Robert Gagnon, and Louis Taillefer, "A Study of Vortex Movements Parallel and Perpendicular to Twin Boundaries in YBCO." Presented at the XXI Int. Conf. on Low Temperature Phys. (LT21), Prague, Czech Republic, Aug. 8-14, 1996. Departement de Physique and Centre de Recherche en Physique du Solide, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1, CANADA; e-mail maubin@pauli.physique.usherb.ca.
F. Auguste, A. Rulmont, N. Vandewalle, H. Bougrine, J. Mucha, M. Ausloos, and R. Cloots, "Microstructure Development in Isothermally Melt-Textured 123-211 Composite Materials." Presented at the Int. Conf. on Physics and Chemistry of Molecular and Oxide Superconductors (MOS'96), Karlsruhe, Germany, August 2-6, 1996. S.U.P.R.A.S., Chemistry Institute B6, University of Liege, Sart -Tilman, B- 4000 Liege, BELGIUM; R. Cloots' e-mail cloots@gw.unipc.ulg.ac.be.
M. Ausloos, N. Vandewalle, H. Bougrine, Ph. Vanderbemden, N. Mineur, and R. Cloots, "Electrical Properties and Microstructure of Magnetically Textured Composite DyBa2Cu3O7-x Ceramics." To be presented at the Int. Conf. on Electronic Ceramics & Applications, Aveiro, Portugal, September 2-4, 1996. S.U.P.R.A.S., Institute of Physics B5, University of Liege, B-4000 Liege, BELGIUM; R. Cloots' e-mail cloots@gw.unipc.ulg.ac.be.
J. Axnaes, W. Holm, Yu. Eltsev, and OE. Rapp, "Sign Change of c-Axis Magnetoconductivity in YBa2Cu3O7-d Single Crystals." To be published in Phys. Rev. Lett. Department of Solid State Physics, Royal Institute of Technology, S-100 44 Stockholm, SWEDEN; telephone +46 8 790 78 71; telefax +46 8 790 69 52; e-mail johan@ftf.kth.se. 73.50.Jt; 74.40.+k; 74.72.Bk.
U. Balachandran and A. N. Iyer, "Status of High-Tc Superconductors." To be published in Mater. Tech. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov.
S. K. Bandyopadhyay, Pintu Sen, P. Barat, Udayan De, K. Mandal, S. K. Kar, and C. K. Majumdar, "Alpha Irradiation of Bi-2212 Superconductor." To be published in Physica C (in press). Contact C. K. Majumdar, S. N. Bose National Centre for Basic Sciences, JD Block, Sector-III, Salt Lake, Calcutta 700 091, INDIA; telefax +91 33 334 3477. Key words: Bi-2212 single crystal, alpha-irradiation, oxygen knock out, interlayer coupling.
M. Baran, V. Dyakonov, I. Fita, L. Gladczuk, A. Wisniewski, and H. Szymczak, "Pressure-Induced Oxygen-Ordering Processes in GdBa1.5Sr0.5Cu3O6+x." To be published in Physica C (in press). Institute of Physics, Polish Academy of Sciences, Al. Lotnik0w 32/46, PL 02-668 Warsaw, POLAND; telefax +48 22 43 09 26; e-mail baran@ifpan.edu.pl. Key words: oxygen ordering, pressure effect, hysteresis, GdBa1.5Sr0.5Cu3O6+x.
J. Bok and J. Bouvier, "Tunneling in Anisotropic Gap Superconductors." Submitted to Phys. Rev. B. Laboratoire de Physique du Solide, UPR 5 CNRS, Ecole Superieure de Physique et Chimie Industrielles de la Ville de Paris, 10 rue Vauquelin, F-75231 Paris Cedex 05, FRANCE; telephone +33 1 40 79 44 51; telefax +33 1 40 79 44 25; e-mail julien.bok@espci.fr. Key words: superconductivity, anisotropic gap, van Hove singularites, tunneling spectroscopy. 74.20.-z; 74.20.Fg; 74.50.+r; 74.70.Vy.
A. T. Boothroyd, A. Mukherjee, and A. P. Murani, "Evidence for Extreme Gap Anisotropy in Ho0.1Y0.9Ba2Cu3O7 from Neutron Spectroscopy of Ho^[3+]." To be published in Phys. Rev. Lett. Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU, UNITED KINGDOM; telelphone +44 1865 272-376 or -200; telefax, +44 1865 272 400; e-mail a.boothroyd1@physics.oxford.ac.uk. 74.72.Bk; 74.25.Ha; 76.30.Kg; 76.20.+q.
S. A. Carter, B. Batlogg, R. J. Cava, J. J. Krajewski, W. F. Peck, Jr., and T. M. Rice, "Hole Doping of the CuO2 Chains in (La,Sr,Ca)14Cu24O41." Submitted to Phys. Rev. Lett. AT&T Bell Laboratories, Murray Hill, NJ 07974.
L. Cattaneo, M. Celasco, A. Masoero, P. Mazzetti, I. Puica, and A. Stepanescu, "Current Noise in HTC Polycrystalline Superconductors: A Comparison Between Experiments and Different Types of Percolation Models." To be published in Physica C (in press). Contact P. Mazzetti, Istituto Elettrotecnico Nazionale Galileo Ferraris and INFM, Torino, ITALY; telefax +39 11 564 73 99. Key words: fluctuation effects, type-II superconductors, electrical resistivity.
R. J. Cava, H. W. Zandbergen, J. J. Krajewski, T. Siegrist, H. Y. Hwang, and B. Batlogg, "Ln3Cu4P4O2: A New Transition Metal Pnictide Oxide Structure Type." Submitted to J. Solid State Chem. Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974.
Bai-Hao Chen, "Introduction of a Tolerance Factor for the Nd2CuO4 (T')-Type Structure." To be published in J. Solid State Chem. Lamont-Doherty Earth Observatory, Columbia University, P.O. Box 1000, Route 9W, Palisades, NY 10964-8000; telephone (914) 359-2900.
G. W. Crabtree, U. Welp, W. K. Kwok, J. A. Fendrich, and B. W. Veal, "The Equilibrium Vortex Melting Transition in YBa2Cu3O7." Presented at the 21st Rare Earth Res. Conf. (21st RERC), Duluth, Minnesota, July 7-12, 1996; to be published in J. Alloys & Compounds. Argonne National Laboratory, MSD 223, Argonne, IL 60439; telephone (708) 252-5509; telefax (708) 252-7777; e-mail crabtree@anl.gov. Key words: vortex, melting, magnetization, resistivity.
Dragomir Davidovic, Suman Kumar, Daniel H. Reich, Jeffrey Siegel, S. B. Field, R. C. Tiberio, R. Hey, and K. Ploog, "Magnetic Correlations, Geometrical Frustration, and Tunable Disorder in Arrays of Superconducting Rings." Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218. 74.25.Ha; 05.50.+q; 74.55.+h; 75.50.Ee.
T. D. Dzhafarov, A. Varilci, M. Sadygov, and M. Altunbas, "The Effect of Ag Diffusion on Properties of BiPbSrCaCuO Thin Films." To be published in Physica C (in press). Contact M. Altunbas, Department of Physics, Faculty of Science and Arts, Karadeniz Technical University, 61080 Trabzon, TURKEY; telefax +90 462 325 3195.
Deniz Ertas and David R. Nelson, "Irreversibility, Mechanical Entanglement and Thermal Melting in Superconducting Vortex Crystals with Point Impurities." Department of Physics, Harvard University, Cambridge, MA 02138.
H. Frank, R. Stollmann, J. Lethen, R. Mueller, L. V. Gasparov, N. D. Zakharov, D. Hesse, and G. Guentherodt, "Preparation and Magnetic Properties of (Bi,Pb)-1212." To be published in Physica C (in press). Physikalisches Institut, RWTH Aachen, Templergraben 55, D-52056 Aachen, GERMANY. Key words: high-temperature superconductors, anisotropy, flux pinning.
G. Fuchs, G. Krabbes, P. Schaetzle, P. Stoye, T. Staiger, and K.-H. Mueller, "High Trapped Fields in Melt-Textured YBCO Samples." To be published in Physica C (in press). Institut fuer Festkoerper- und Werkstofforschung Dresden, Helmholtzstrasse 20, D-01069 Dresden, GERMANY; telefax +49 351 4659 537. Key words: grain alignment (texturing), application of high-Tc superconductors, critical current density.
D. Fiorani, A. M. Testa, R. D. Zysler, V. Rybachuk, and F. Licci, "Magnetic Properties of La2Cu1-xZnxO4+d." To be published in Physica C (in press). ICMAT-CNR, Area della Ricerca di Roma, C.P. 10, I-00016 Monterotondo Stazione, Rome, ITALY. Key words: normal-state properties, substitution effects, antiferromagnetic order.
J. L. Garcia-Munoz, M. Suaaidi, J. Fontcuberta, S. Pinol, and X. Obradors, "Lattice Compression and Charge Transfer in Electron-Doped L2-xCexCuO4 Superconductors." To be published in Physica C (in press). Institut de Ciencia de Materials de Barcelona-CSIC, Campus UAB, 08193 Bellaterra, Catalunya, SPAIN; telefax +34 3 580 5729; e-mail garcia.munoz@icmab.es. 74.62.Fj; 74.72.Jt; 74.62.Bf.
H. Ghamlouch and M. Aubin, "Additional Nernst Voltage Contribution to the Seebeck Coefficient in YBCO Due to Guided Motion by Twin Planes." To be published in Physica C. Departement de Physique and Centre de Recherche en Physique du Solide, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1, CANADA. 74.25.Fy.
H. Ghamlouch, M. Aubin, R. Gagnon, and L. Taillefer, "Observation of Vortex Lattice Melting in YBCO by Seebeck Effect Measurements." To be published in Phys. Rev. B. Departement de Physique and Centre de Recherche en Physique du Solide, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1, CANADA. 74.25.Fy.
P. Ghigna, G. Spinolo, M. Scavini, G. Chiodelli, G. Flor, and A. V. Chadwick, "Nature and Amount of Carriers in Ce-Doped Nd2CuO4: II. Low Temperature Transport and XAS Characterization." To be published in Physica C (in press). I.N.C.M., Dip. Chimica Fisica, and C.S.T.E./C.N.R., Universita di Pavia, Viale Taramelli 16, I-27100 Pavia, ITALY; telefax +39 382 507 575; e-mail paolo@chifis.unipv.it. Key words: n-type superconductors, Nd2-xCexCuO4+d superconductor, point defect structure, XAFS.
M. Greven, R. J. Birgeneau, and U.-J. Wiese, "A Monte Carlo Study of Correlations in Quantum Spin Ladders." To be published in Phys. Rev. Lett. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139. 75.10.Jm; 75.40.Mg.
Olle Gunnarsson, Erik Koch, and Richard M. Martin, "Mott Transition in Degenerate Hubbard Models: Application to Doped Fullerenes." Max-Planck-Institut fuer Festkoerperforschung, D-70506 Stuttgart, GERMANY. 71.10.Fd; 71.30.+h; 71.20.Tx.
A. K. Gupta, Neeraj Khare, and Sangeeta Khare, "Development of High-Tc Superconducting Thick Film rf-SQUID Sensors and Their Application in Non Destructive Testing." Submitted to Measurement Sci. & Technol. National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi-110012, INDIA; telephone +91 11 578 7161; telefax +91 11 575 2678; e-mail npl@sirnetd.ernet.in.
C. A. Hayward, D. Poilblanc, and L. P. Levy, "The Magnetization of Cu2(C5H12N2)2Cl4: A Heisenberg Spin Ladder System." Laboratoire de Physique Quantique, Universite Paul Sabatier, F-31062 Toulouse, FRANCE. 71.27.+a; 75.10.-b; 75.10.Jm.
Lifang Hou, J. Deak, P. Metcalf, M. McElfresh, and G. Preosti, "Dependence of the Vortex-Solid Phase Transition of YBa2Cu3O7-d Thin Films on Anisotropy: Evidence for a Universal Phase Boundary." Physics Department, Purdue University, West Lafayette, IN 47907. 74.60.Ge; 74.76.Bz.
M. Houssa, H. Bougrine, S. Stassen, R. Cloots, and M. Ausloos, "Superconductivity Fluctuation Effects on the Thermal Conductivity of Bi2Sr2CaCu2O8." To be published in Phys. Rev. B. S.U.P.R.A.S., Institute of Physics B5, University of Liege, B-4000 Liege, BELGIUM; e-mail houssa@gw.unipc.ulg.ac.be. 74.25.Fy; 74.40.+k; 74.72.Hs.
M. Houssa, R. Cloots, S. Stassen, M. Pekala, and M. Ausloos, "Field Dependence of the Electrothermal Conductivity of High-Tc Superconductors." Presented at the XXI Int. Conf. on Low Temperature Phys. (LT21), Prague, Czech Republic, August 8-14, 1996. S.U.P.R.A.S., Institute of Physics, University of Liege, B-4000 Liege, BELGIUM; e-mail houssa@gw.unipc.ulg.ac.be.
Q. Huang, J. W. Lynn, A. Santoro, B. C. Chakoumakos, R. J. Cava, J. J. Krajewski, and W. F. Peck, Jr., "Neutron Powder Diffraction Study of the Nuclear and Magnetic Structures of HoNi1.985Co0.015B2C and HoNiBC." Submitted to Physica C. Contact J. W. Lynn, Reactor Radiation Division, National Institute of Standards and Technology, Bldg. 235, E151, Gaithersburg, MD 20899; telephone (301) 975-6246; telefax (301) 921-9847; e-mail jeff@rrdstrad.nist.gov.
Z. Jirak, J. Hejtmanek, K. Knizek, and R. Sonntag, "Carbonate Groups and the Superconductivity in 123 Cuprates Y0.8Ca0.2Ba2Cu3-xCxOy." To be published in Physica C (in press). Institute of Physics, Cukrovarnicka 10, CR-162 00 Prague 6, CZECH REPUBLIC. Key words: ac susceptibility, electrical resistivity, thermoelectric power, neutron diffraction, Y0.8Ca0.2Ba2Cu3-xCxOy.
Ch. Jooss, A. Forkl, and H. Kronmueller, "Simple Model of Vortex Pinning at Rough Superconductor Surfaces in YBa2Cu3O7-d Thin Films." To be published in Physica C (in press). Contact H. Kronmueller, Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; telefax +49 711 689 1912.
Neeraj Khare, "Symmetry of Order Parameter of High-Tc Superconductors." National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi-110012, INDIA; telephone +91 11 578 7161; telefax +91 11 575 2678; e-mail npl@sirnetd.ernet.in.
Neeraj Khare, A. K. Gupta, Sangeeta Khare, L. C. Gupta, R. Nagarajan, Z. Hossain, and R. Vijayaraghavan, "rf-SQUID Effect in YNi2B2C Due to Natural Grain Boundary Weak Links." Submitted to Appl. Phys. Lett. National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi-110012, INDIA; telephone +91 11 578 7161; telefax +91 11 575 2678; e-mail npl@sirnetd.ernet.in.
Neeraj Khare, A. K. Gupta, Sangeeta Khare, H. K. Singh, A. K. Saxena, and O. N. Srivastava, "Hg(Tl)-Ba-Ca-Cu-O High-Tc Thin Film rf-SQUID Operating Above 115 K." Submitted to Appl. Phys. Lett. National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi-110012, INDIA; telephone +91 11 578 7161; telefax +91 11 575 2678; e-mail npl@sirnetd.ernet.in.
Neeraj Khare, A. K. Gupta, S. K. Shrivastava, Sangeeta Khare, V.P.N. Padmanaban, "High-Tc Thick Film Magnetic Field Sensor Based on Harmonic Generation Effects." Submitted to Measurement Sci. & Technol. National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi-110012, INDIA; telephone +91 11 578 7161; telefax +91 11 575 2678; e-mail npl@sirnetd.ernet.in.
R. A. Klemm, "Some Improved Geometries for Josephson Junction Investigations of the Order Parameter Symmetry in High-Tc 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. 74.50.+r; 74.72.-h.
Vladimir N. Kostur and Philip B. Allen, "Polaron and Bipolaron Formation in a Cubic Perovskite Lattice." Department of Physics, State University of New York, Stony Brook, NY 11794-3800. 71.38.+i; 71.30.+h; 63.20.-e.
JuYoung Lee, Young Hwan Kim, Taek-Sang Hahn, and Sang Sam Choi, "Determining the Absolute Value of Penetration Depth of Large Area Films." To be published in Appl. Phys. Lett., Sept. 1996. Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul, KOREA; telefax +82 2 988 5789; e-mail juylee@kistmail.kist.re.kr. 74.25.Nf.
A. Lombardi, M. Mali, J. Roos, and D. Brinkmann, "Hyperfine Fields at the Ba Site in YBa2Cu4O8: An NMR and NQR Study." To be published in Physica C (in press). Physik-Institut, Universitaet Zurich, CH-8057 Zurich, SWITZERLAND. Key words: NMR, NQR, YBa2Cu4O8.
D. Maier, H. Rothermel, K. H. Gundlach, and R. Zimmerman, "Submicron Nb-Al/Al Oxide-Nb Tunnel Junctions Sandwiched Between Al Films." To be published in Physica C (in press). Institut de Radio Astronomie Millimetrique, 300 Rue de la Piscine, F-38406 St. Martin D'Heres, FRANCE. Key words: electrical resistivity, Josephson effect, microwave absorption, mixer, tunneling.
S. Majumder, D. R. Jackson, and M. Guglielmi, "Spectral Gaps for Leaky Waves on a Periodic Structure." Preprint #96:077; submitted to IEEE Trans. Microwave Theory & Tech. 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..
A. A. Maksimov, I. I. Tartakovskii, D. A. Pronin, S. V. Zaitsev, G. Blumberg, M. V. Klein, M. Karlow, S. L. Cooper, B. W. Veal, and A. P. Paulikas, "Influence of Oxygen Ordering on Raman Scattering and Reflectivity Spectra in YBa2Cu3O6.4 Single Crystals." 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.
H. Michor, R. Krendelsberger, G. Hilscher, E. Bauer, C. Dusek, R. Hauser, L. Naber, D. Werner, P. Rogl, and H. W. Zandbergen, "Superconducting Properties of La3Ni2B2N3-d." Submitted to Phys. Rev. B. Institut fuer Experimentalphysik, Technische Universitaet Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, AUSTRIA. 74.25.Bt; 74.62.Fj; 74.72.Yg; 63.20.Kr.
Toshiharu Minamikawa, Mitsutoshi Tazoe, Kazuhito Segawa, Yasuto Yonezawa, Akiharu Morimoto, and Tatsuo Shimizu, "Preparation of a-Axis-Oriented YBa2Cu3Ox Superconducting Films on MgO Substrates with PrBa2Cu3Ox Buffer Layers." To be published in Physica C (in press). Contact Akiharu Morimoto, Department of Electrical and Computer Engineering, Faculty of Engineering, Kanazawa University, Kanazawa 920, JAPAN. Key words: a-axis orientation, YBa2Cu3Ox superconducting films, MgO substrates, PrBa2Cu3Ox buffer layer, pulsed laser ablation.
C. P. Moca and M. Crisan, "Marginal Behavior of a Two Dimensional Fermionic System with Saddle Points." To be published in J. Supercond. Department of Theoretical Physics, University of Cluj, 3400-Cluj, ROMANIA.
V. N. Morgoon, V. Bindilatti, A. V. Bondarenko, D. Rodrigues, Jr., and A. V. Sivakov, "Crossover Point in the Magnetic Phase Diagram of YBa2Cu3O7-d with Twin Planes." Presented at the XXI Int. Conf. on Low Temperature Phys. (LT21), Prague, Czech Republic, August 8-14, 1996; to be published in Czechoslovak J. Phys., Vol. 46, S3, 1573 (1996). Material Engineering Department, FAENQUIL/DEMAR, Polo Urbo-Industrial, Gleba AI-6, CEP-126.600-000, Lorena SP, BRAZIL; telephone +55 12 553 31 74; telefax +55 12 553 30 06; e-mail ftilor@eu.ansp.br or dobras@morgun.kharkov.ua.
V. N. Morgoon, V. A. Shklovskij, V. Bindilatti, A. V. Bondarenko, R. F. Jardim, C. C. Becerra, A. F. Sartori, and A. V. Sivakov, "Guided Vortex Motion in YBa2Cu3O7-d Single Crystals with Unidirectional Twins." Presented at the XXI Int. Conf. on Low Temperature Phys. (LT21), Prague, Czech Republic, August 8-14, 1996; to be published in Czechoslovak J. Phys., Vol. 46, S3, 1751 (1996). Material Engineering Department, FAENQUIL/DEMAR, Polo Urbo-Industrial, Gleba AI-6, CEP-126.600-000, Lorena SP, BRAZIL; telephone +55 12 553 31 74; telefax +55 12 553 30 06; e-mail ftilor@eu.ansp.br or dobras@morgun.kharkov.ua.
V. N. Morgoon, V. A. Shklovskij, V. Bindilatti, A. V. Bondarenko, R. F. Jardim, C. C. Becerra, C. Y. Shigue, and A. V. Sivakov, "Mixed State Odd Effect in YBa2Cu3O7-d with Unidirectional Twins." To be published in J. Low Temp. Phys.: Proc. of the Int. Conf. on Phys. and Chem. of Molecular and Oxide Supercond. (MOS'96), Karlsruhe, Germany, August 2-6, 1996. Material Engineering Department, FAENQUIL/DEMAR, Polo Urbo-Industrial, Gleba AI-6, CEP-126.600-000, Lorena SP, BRAZIL; telephone +55 12 553 31 74; telefax +55 12 553 30 06; e-mail ftilor@eu.ansp.br or dobras@morgun.kharkov.ua. 74.60.-w; 74.60.Ec; 74.60.Ge.
Akiharu Morimoto, Hiromichi Kawasaki, Toshiharu Minamikawa, and Tatsuo Shimizu, "Microwave-Modulated Nonresonant Microwave Absorption in YBa2Cu3Ox High-Tc Superconductors." To be published in Physica C (in press). Department of Electrical and Computer Engineering, Faculty of Engineering, Kanazawa University, Kanazawa 920, JAPAN; telefax +81 762 34 4900; e-mail amorimot@ec.t.kanazawa-u.ac.jp. Key words: YBa2Cu3Ox superconductors, nonresonant microwave absorption, microwave modulation, field modulation, quenched and melt-growth sample.
V. V. Moshchalkov, X. G. Qiu, and V. Bruyndoncx, "The Paramagnetic Meissner Effect Resulting from the Persistence of the Giant Vortex State." To be published in J. Low Temp. Phys.: Proc. of the Int. Conf. on Phys. and Chem. of Molecular and Oxide Supercond. (MOS'96), Karlsruhe, Germany, August 2-6, 1996. Lab. voor Vaste-Stoffysika en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, BELGIUM; telephone +32 16 32 76 18; telefax +32 16 32 79 83; e-mail victor.moshchalkov@fys.kuleuven.ac.be. 74.60.Ec; 74.25.Ha; 74.60.Ge; 74.62.Bf.
Y. Namikawa and Y. Shiohara, "Growth Rate Anisotropy of YBa2Cu3O7-x Single Crystals in the Pulling Method." To be published in Physica C (in press). Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone +81 6 466 5593 or +81 3 3536 5711; telefax +81 6 466 5733 or +81 3 3536 5705. Key words: single-crystal growth of YBa2Cu3O7-x, growth rate, pulling method, surface morphology.
Yuri N. Obukhov and Franz E. Schunck, "Regular Solutions in Abelian Gauge Model." Institute for Theoretical Physics, University of Cologne, D-50923 Koeln, GERMANY; e-mail yo@thp.uni-koeln.de. 03.50.-z; 11.15.Kc; 74.20.De; 74.60.-w.
Yuri N. Obukhov and Franz E. Schunck, "Vortices, Flux Tubes and Other Structures in the Ginzburg-Landau Model: A Possible Fine Structure of the Mixed State?" Institute for Theoretical Physics, University of Cologne, D-50923 Koeln, GERMANY; e-mail yo@thp.uni-koeln.de; preprint also available at hep-th@xxx.lanl.gov (#9606131). 03.50.-z; 11.15.Kc; 74.20.De; 74.60.-w.
C. O'Donovan, M. D. Lumsden, B. D. Gaulin, and J. P. Carbotte, "c-Axis Josephson Tunnelling in Twinned and Untwinned YBCO-Pb Junctions." Submitted to Phys. Rev. B. Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, CANADA; preprint also available at cond-mat@xxx.lanl.gov (#9607125).
M. Pekala, H. Bougrine, M. Houssa, M. Ausloos, J. Mucha, S. Stassen, and R. Cloots, "Electrical, Thermoelectrical and Thermal Transport Properties of BSCCO Ceramics." To be presented at the Int. Conf. on Electronic Ceramics & Applications, Aveiro, Portugal, September 2-4, 1996. S.U.P.R.A.S., Montefiore Electricity Institute B-28, University of Liege, Liege, BELGIUM.
D. Poilblanc, H. Endres, F. Mila, M. G. Zacher, S. Capponi, and W. Hanke, "One-Particle Interchain Hopping in Coupled Hubbard Chains." Laboratoire de Physique Quantique, Universite Paul Sabatier, F-31062 Toulouse, FRANCE. 71.27.+a; 71.38.+i; 74.20.Mn; 74.25.Kc.
D. Ponnusamy, Y. Coulter, M. Daugherty, K. Ravi-Chandar, and K. Salama, "Processing of BSCCO Superconducting Rods for Current Leads." Preprint #96:084; submitted to Appl. Supercond. 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.
M. Preda and H. Stenschke, "Electromagnetic Binding of a Vortex Line to a Spherical Cavity in a Superconductor." To be published in Physica C (in press). Fachbereich Physik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin, GERMANY; e-mail preda@vax.1physik.fu-berlinde. Key words: flux pinning.
A. L. Rakhmanov and A. V. Rozhkov, "Electric Field Effect on Critical Current of SNS Contact." To be published in Physica C (in press). Contact A. V. Rozhkov, Scientific Center for Applied Problems in Electrodynamics, Russian Academy of Sciences, 174122, Izhorskaya Str. 13/19, Moscow, RUSSIA. 74.50.+r; 74.25.Nf.
E. Sudhakar Reddy and T. Rajasekharan, "Mechanisms for Microstructural Evolution in Melt Processed Cu-59 wt. % Sn and YBa2Cu3O7." Submitted to Phys. Rev. B. Defence Metallurgical Research Laboratory, P.O. Kanchanbagh, Hyderabad - 500 058, INDIA; telefax +91 40-239683 or - -218439; e-mail vsbsp@vohyd.ernet.in. Key words: peritectic reaction, melt growth, microstructure, Cu-Sn, YBa2Cu3O7. 74.80.Bj; 81.30.-t; 81.40.-z.
Z. F. Ren, J. H. Wang, and D. J. Miller, "The Structural Symmetry of Epitaxial Tl2Ba2CuO6+d Thin Films." Submitted to Appl. Phys. Lett. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov.
J. M. Repaci, C. Kwon, Qi Li, Xiuguang Jiang, T. Venkatessan, R. E. Glover III, C. J. Lobb, and R. S. Newrock, "Absence of a Kosterlitz-Thouless Transition in Ultra-Thin YBa2Cu3O7-d Films." Submitted to Phys. Rev. B. Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742; C. J. Lobb's telephone (301) 405-6130; telefax (301) 314-9541; e-mail lobb@squid.umd.edu. 74.25.Fy; 74.72.Bk; 74.76.Bz.
J. J. Rodriguez-Nunez, C. E. Cordeiro, and A. Delfino, "Moment Approach for the 2D Attractive Hubbard Model." To be published in Physica A. Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea S/N, Boa Viagem, 24210-340, Niteroi, Rio de Janeiro, BRAZIL; telephone +55 21 620 6735; telefax +55 21 620 2034; e-mail jjrn@if.uff.br; preprint also available at Preprint Requests, Biblioteca do Instituto de Fisica, Preprint Requests, Av. Litoranea S/N, Boa Viagem, 24210-340 - Niteroi, Rio de Janeiro, BRAZIL; e-mail bifisica@if.uff.br or ndcbifi@vmhpo.uff.br. 74.20.Fg; 74.10.-z; 74.60.-w; 74.72.-h.
N. L. Saini, A. Lanzara, A. Bianconi, H. Oyanagi, H. Yamaguchi, K. Oka, and T. Ito, "Temperature Dependent Cu-O Distribution Function of the Superconducting CuO2 Plane." To be published in Physica C (in press). Dipartimento di Fisica, Universita di Roma "La Sapienza", P. A. Moro 2, I-00185 Roma, ITALY. Key words: superconductivity, x-ray absorption, pair distribution function, local structure. 78.70.Dm; 71.28.+d; 74.70.Vy.
T. Sakai, D. Poilblanc, and D. J. Scalapino, "Hole Pairing and Phonon Dynamics in Generalized 2D t-J-Holstein Models." Laboratoire de Physique Quantique, Universite Paul Sabatier, F-31062 Toulouse, FRANCE. 71.27.+a; 71.38.+i; 74.20.Mn.
Alvaro Sanchez and Carles Navau, "Magnetic Levitation of Thin Superconducting Disks." Grup d'Electromagnetisme, Departament de Fisica, Universitat Autonoma Barcelona, 08193 Bellaterra, Barcelona, SPAIN; telephone +34 3 581 2961; telefax +34 3 581 1350; e-mail alvar@elema.uab.es. 85.25.Ly; 74.25.Ha; 74.60.Jg.
Alvaro Sanchez and Carles Navau, "Vertical Force, Magnetic Stiffness, and Damping for Levitating Type-II Superconductors." To be published in Physica C. Grup d'Electromagnetisme, Departament de Fisica, Universitat Autonoma Barcelona, 08193 Bellaterra, Barcelona, SPAIN; telephone +34 3 581 2961; telefax +34 3 581 1350; e-mail alvar@elema.uab.es. Key words: levitation, applications of high-Tc superconductors, magnetization.
Osvaldo F. Schilling, Luis Ghivelder, and I. Abrego Castillo, "Two-Fluid Critical-State Model for the Description of ac Susceptibility of Ceramic High-Tc Superconductors." Submitted to J. Appl. Phys. Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario, Trindade, 88040-900, Florianopolis, Santa Catarina, BRAZIL; e-mail fsc1fre@fsc01.fsc.ufsc.br.
G. M. Schmiedeshoff and J. L. Smith, "Supercritical Behavior of the Mixed State of Nb-Ti in High Magnetic Fields." To be published in Phil. Mag. B. Department of Physics, Occidental College, Los Angeles, CA 90041.
Minako Shida, Eriko Ohshima, Masae Kikuchi, Masayasu Nagoshi, and Yasuhiko Syono, "Valence Analysis of Pb and Cu and Superconductivity of (Pb,Cu)(Sr,La)2CuOy." To be published in Physica C (in press). Institute for Materials Research, Tohoku University, Katahira, Aoba-ku, Sendai, 980-77, JAPAN. Key words: (Pb,Cu)(Sr,La)2CuOy, HIP treatment, Pb valence analysis, oxygen analysis, overdoping.
J. P. Singh, "Composite Ag-Sheathed Bi(Pb)-Sr-Ca-Cu-O Superconducting Tapes with Enhanced Strain Tolerance." Submitted to Ceramic Technology International. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov.
Mads Peter Sorensen and J. J. Rodriguez-Nunez, "Anomalous Superconductivity in the Traditional t-J Model: Moment Approach." Submitted to Physica C. Institute of Mathematical Modelling, Technical University of Denmark, Building 321, DK-2800 Lyngby, DENMARK; J. J. Rodriguez-Nunez's telephone +55 21 620 6735; telefax +55 21 620 2034; e-mail jjrn@if.uff.br; preprint also available at Preprint Requests, Biblioteca do Instituto de Fisica, Av. Litoranea S/N, Boa Viagem, 24210-340 - Niteroi, Rio de Janeiro, BRAZIL; e-mail bifisica@if.uff.br or ndcbifi@vmhpo.uff.br. 74.20.Fg; 74.10.-z; 74.60.-w; 74.72.-h.
S. Sridhar, S. Oxx, Balam A. Willemsen, H. Srikanth, and D. P. Choudhury, "Comment on 'Vortex Glass and Lattice Melting Transitions in a YNi2B2C Single Crystal.'" Submitted to Phys. Rev. Lett. Department of Physics, Northeastern University, 360 Huntington Ave., Boston, MA 02115. 74.60.Ec; 74.25.Fy; 74.60.Ge; 74.70.Ad.
S. Stassen, A. Rulmont, M. Ausloos, and R. Cloots, "Non-Isovalent Metal Substitution for Bismuth, Strontium, Calcium, and Copper in Bi-Based 2212 Superconducting Ceramics." Presented at the Int. Conf. on Physics and Chemistry of Molecular and Oxide Superconductors (MOS'96), Karlsruhe, Germany, August 2-6, 1996. S.U.P.R.A.S., Chemistry Institute B6, University of Liege, Sart -Tilman, B-4000 Liege, BELGIUM; R. Cloots' e-mail cloots@gw.unipc.ulg.ac.be.
S. Stassen, A. Rulmont, H. Bougrine, M. Ausloos, and R. Cloots, "Non-Isovalent Chemical Substitutions of Rare Earth Ions in Bi-Based 2223 Bulk Superconducting Materials." To be presented at the Int. Conf. on Electronic Ceramics & Applications, Aveiro, Portugal, September 2-4, 1996. S.U.P.R.A.S., Chemistry Institute B6, University of Liege, Sart - -Tilman, B-4000 Liege, BELGIUM; R. Cloots' e-mail cloots@gw.unipc.ulg.ac.be.
Y. S. Sung, X. F. Zhang, P. J. Kostic, and D. J. Miller, "The Effects of Carbon on TlBa2Ca2Cu3Ox Phase Formation in the TlF-Ba2Ca2Cu3Oz System." Submitted to Appl. Phys. Lett. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov.
H. Szymczak, M. Baran, S. L. Gnatchenko, R. Szymczak, Y. F. Chen, Z. G. Ivanov, and L.-G. Johansson, "Metastable Photoinduced Changes in the Magnetic Properties of Tl2Ba2CaCu2O8 Thin Films." To be published in Europhys. Lett. Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02-668 Warsaw, POLAND. 74.25.Ha; 74.72.Fq; 74.62.Dh.
Y. Tanaka, M. Ishizuka, L. L. He, S. Horiuchi, and H. Maeda, "Jc Property and Microstructure of Bi2223 Tapes Made Using AgCu Alloy Sheaths Doped with Ti, Zr or Hf." To be published in Physica C (in press). National Research Institute for Metals, 1-2-1 Sengen, Tsukuba 305, JAPAN; telefax +81 298 53 1202; e-mail tanakayo@nrim.go.jp. Key words: Bi-2223 tape, introduction of flux pinning center, amorphous region.
V. R. Todt, X. F. Zhang, D. J. Miller, M. St. Louis-Weber, and V. P. Dravid, "Controlled Growth of Bulk Bicrystals for the Investigation of Microstructure-Property Relations of YBa2Cu3Ox Grain Boundaries." Submitted to Appl. Phys. Lett. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov.
A. Vailionis, A. Brazdeikis, and A. S. Flodstroem, "Microstructural Properties of Bi2Sr2Can-1CunOy Multilayers Grown by Molecular Beam Epitaxy." Submitted to J. Appl. Phys. Contact A. Brazdeikis, Materials Physics, Department of Physics, Royal Institute of Technology, S-100 44 Stockholm, SWEDEN; telephone +46 8 790 6058; telefax +46 8 24 91 31; audrius@matphys.kth.se.
N. Vandewalle, R. Cloots, and M. Ausloos, "Simulations of the Growth of YBa2Cu3O7-x Superconducting Ceramics." To be presented at the Int. Conf. on Electronic Ceramics & Applications, Aveiro, Portugal, September 2-4, 1996. S.U.P.R.A.S., Institute of Physics B5, University of Liege, B-4000 Liege, BELGIUM; R. Cloots' e-mail cloots@gw.unipc.ulg.ac.be.
A. I. Veinger and A. S. Kheifets, "Magnetic Field Dependent Microwave Absorption in Pure Superconducting Tin near Tc. To be published in Physica C (in press). Contact A. S. Kheifets, Electronic Structure of Materials Centre, School of Physical Sciences, Flinders University of South Australia, G.P.O. Box 2100, Adelaide 5001, AUSTRALIA; telefax +61 8 201 2905; e-mail anatoli@esm.ph.flinders.edu.au.
N. V. Vo, H. K. Liu, and S. X. Dou, "Critical Current Densities of High-Tc Bi(Pb)-2223 Wire-In-Tube, Continuous-Tube-Forming/Filling Silver-Alloy Double-Pancake Coils at 77 K." Submitted to Appl. Superconductivity. Centre for Superconducting and Electronic Materials, Institute of Materials Technology and Manufacturing, University of Wollongong, Northfields Ave., Wollongong, NSW 2522, AUSTRALIA; e-mail nvv01@uow.edu.au.
N. L. Wang, B. Buschinger, C. Geibel, and F. Steglich, "Crystal Growth and Anisotropic Resistivity of Bi2Sr2-xLaxCuOy." To be published in Phys. Rev. B, Vol. 54, No. 10, Sept. 1996. Institut fuer Festkoerperphysik, Technische Hochschule Darmstadt, Hochschulstrasse 8, D-64289 Darmstadt, GERMANY. 74.25.Fy; 74.72.Hs; 72.15.Eb.
N. L. Wang, B. Buschinger, C. Geibel, and F. Steglich, "Temperature Dependence of the In-Plane Resistivity in Underdoped Bi2Sr2CaCu2Oy Single Crystals." To be published in Phys. Rev. B, Vol. 54, No. 10, Sept. 1996. Institut fuer Festkoerperphysik, Technische Hochschule Darmstadt, Hochschulstrasse 8, D-64289 Darmstadt, GERMANY. 74.25.Fy; 74.72.Hs; 72.15.Eb.
J. C. Wei, J. L. Chen, L. Horng, and T. J. Yang, "Thickness Dependence of Magnetic Force and Vortex Creation in Type-II Superconducting Thin Film." To be published in Physica C (in press). Contact T. J. Yang, Department of Electro-Physics, National Chiao-Tung University, Hsinchu, Taiwan, REPUBLIC OF CHINA; telefax +886 35 725 230. Key words: type-II superconductors, thin films.
K. Widder, D. Berner, J. Muenzel, H. P. Geserich, M. Klaeser, G. Mueller-Vogt, and Th. Wolf, "Charge Carrier Distribution in Y1-zCazBa2Cu3Ox." To be published in Physica C (in press). Institut fuer Angewandte Physik, Universitaet Karlsruhe, D-76128 Karlsruhe, GERMANY; telefax +49 351 4659 537; e-mail widder@ifw-dresden.de. 74.72.Bk; 74.25.Gz; 74.62.Dh.
J. Wiesner, C. Traeholt, J.-G. Wen, H.-W. Zandbergen, G. Wirth, and H. Fuess, "High Resolution Electron Microscopy of Heavy-Ion Induced Defects in Superconducting Bi-2212 Thin Films in Relation to Their Effect on Jc." To be published in Physica C (in press). Contact C. Traeholt, Laboratory of Materials Science, Delft University of Technology NCHREM, 137 Rotterdamseweg, 2628 AL Delft, THE NETHERLANDS; telefax +31 15 78 6730.
P. Wochner, X. Z. Xiong, and S. C. Moss, "In-Plane Stripe Order and Superconductivity in Phase-Separated and Staged Single Crystal La2CuO4+d." Preprint #96:085; submitted to Nature. 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.
Th. Wolf, "Crystal Growth Mechanisms and Growth Anisotropy of YBa2Cu3Ox Crystals." To be published in J. Cryst. Growth. Forschungszentrum Karlsruhe, Institut fuer Technische Physik, Postfach 3640, D-76021 Karlsruhe, GERMANY; telephone +49 7247 82 4885; telefax +49 7247 82 2849.
W. Xu, Y. Ren, and C. S. Ting, "Ginzburg-Landau Equations for a Mixed s+d Symmetry Superconductor with Nonmagnetic Impurities." Preprint #96:080; submitted to Phys. Rev. B. 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.
K. Yamada, J. Wada, K. Kurahashi, C. H. Lee, Y. Kimura, S. Wakimoto, Y. Endoh, S. Hosoya, G. Shirane, R. J. Birgeneau, and M. A. Kastner, "Doping Dependence of the Spatially Modulated Dynamical Spin Correlations and the Superconducting Transition Temperature in La2-xSrxCuO4." Submitted to Phys. Rev. Lett. Department of Physics, Tohoku University, Aramaki Aoba, Sendai 980-77, JAPAN. 74.72.Dn; 75.10.Jm; 75.50.Ee.
Z. Yamani and M. Akhavan, "Role of Pr Substitution as Deoxygenation in Suppression of Superconductivity in GdPr-123 System." To be published in Physica C (in press). Magnet Research Laboratory, Department of Physics, Sharif University of Technology, P. O. Box 11365-9161, Teheran, IRAN. Key words: Gd1-xPrxBa2Cu3O7-y, Pr-doping, transport properties, Tc suppression, oxygen depletion.
F. Yu, V. N. Kopylov, M. B. Salamon, N. N. Kolesnikov, M. A. Hubbard, H. M. Duan, and A. M. Hermann, "Field Dependent Thermal Conductivity of Tl2Ba2CuO6: Evidence for Andreev Scattering of Quasiparticles." To be published in Physica C (in press). Contact M. B. Salamon, Department of Physics and Science and Technology Center for Superconductivity, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL 61801-3080; telefax (217) 244-2278. Key words: thermal conductivity, vortex lines, Andreev reflection.
C. C. Yuan, D. S. Wu, C. M. Wang, and H.-C.I. Kao, "Superconductivity of La1.5-x/2SrxBa1.5-x/2Cu3Oy Compounds." To be published in Physica C (in press). Department of Chemistry, Tamkang University, Tamsui 25137, Taiwan, REPUBLIC OF CHINA. Key words: superconductivity, hole concentration, oxygen stoichiometry, La1.5-x/2SrxBa1.5-x/2Cu3Oy.
X. Z. Zhou, H. P. Kunkel, and Gwyn Williams, "Resistivity, Magnetoresistance and Field-Dependent ac Susceptibility of ErNiBC." To be published in J. Phys. Department of Physics, University of Manitoba, Winnipeg R3T 2N2, CANADA.
(An * indicates a previously listed event.)
Aug. 27, 1996: Special Session on HTS Coated Conductors: 1996 Applied Superconductivity Conference, Doubletree Hotel, Pittsburgh. The Materials Program is planning a special "rump" session on the state-of-the-art in HTS coated conductors. Purpose of this informal session is to promote discussion on different techniques being developed to make high-current coated conductors, and to discuss how (or whether) these might ultimately be scaled up to make long lengths of wire. Open to all interested. Will be held in parallel with a similar session on HTS Josephson junctions (see below). For information, contact David Rudman, Program National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80303; telephone (303) 497-5081; telefax (303) 497-3042; e-mail rudman@boulder.nist.gov.
Aug. 27, 1996: Special Session on HTS Josephson Junctions: 1996 Applied Superconductivity Conference, Doubletree Hotel, Pittsburgh.The Electronics Program of ASC'96 is planning a special evening session on the state-of-the-art in HTS Josephson junctions and related technologies. Purpose of this informal session will be to promote discussion on the challenges in developing Josephson-junction circuits in HTS materials, potential applications, and the hurdles encountered in making applications a reality. Session will feature very short talks followed by an equal amount of discussion. Will be held in parallel with a similar session on HTS Coated Conductors run by the Materials Program (see last entry). For further information, contact Ronald Ono, Division 814.03, National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80303; telephone (303) 497-3762; telefax (303) 497-3042; e-mail ono@boulder.nist.gov.
Dec. 8 - 12, 1996: International Conference on Stripes, Lattice Instabilities, and High Tc Superconductivity, Rome, Italy. Purpose of this conference is to provide an opportunity to discuss the rapidly expanding experimental data showing mesoscopic structure and lattice anomalies in high-temperature superconductors and related theoretical works relevant to high-Tc superconductivity. The following topics will be included: lattice instabilities (static and dynamic fluctuations), superconductivity in inhomogeneous lattices, experimental and theoretical components, stripe structures at mesoscopic scales, phase separation, superstructures, intrinsic Josephson effect, superconductivity in low dimension, superconductivity in artificial modulated structures, and quantum Hall effect and superconductivity. Invited or contributed oral presentations and posters. For information, contact Antonio Bianconi, Dipartimento di Fisica, Universita' di Roma "La Sapienza", P. le Aldo Moro, 2, 00185 Roma, Italy; telephone +39 6 4991-4405 or -4612; telefax +39 6 -4957697 or -4463158; e-mail bianconie@roma1.infn.it. Information also available a the URL http://g4risc.roma1.infn.it/confhome.it.
March 31- April 1, 1997: 1997 Workshop on ac Losses, San Francisco Marriott, San Francisco, CA. Sponsored by the Electric Power Research Institute (EPRI). Sequel to the workshop held in San Francisco on 1995; will cover theoretical and experimental research on power-line frequency (50-60 Hz) ac losses in high-temperature superconductors, and the influence such losses have on the design of HTSC devices for electric power applications. Program will consist of talks, posters, and workshop discussions. No registration fee, but attendance limited to 50 participants. Workshop will be in parallel with but separate from the 1997 MRS Spring Meeting being held March 31 - April 4, 1997, at the same location. For further information, contact one of the workshop organizers, preferably by e-mail: John R. Clem, A517 Physics, Iowa State University, Ames, IA 50011, phone (515) 294-4223, fax (515) 294-0689, e-mail clem@ameslab.gov; or Masaki Suenaga, Brookhaven National Laboratory, Bldg. 480, Upton, NY 11973, phone (516) 344-3518, fax (516) 344-4071, e-mail mas@bnlux1.bnl.gov.
May 4 - 9, 1997: Fourth Symposium on Low Temperature Electronics and High Temperature Superconductivity, 191st Electrochemical Society Meeting, Montreal, Canada. Intended to provide a forum for discussion of latest developments in the field. Will focus on new aspects of electronic materials, devices, and systems operating at cryogenic temperatures. Contributed papers are solicited in the following areas: 1) Fundamentals: theoretical limitations and restrictions and superconducting materials; 2) Devices: semiconductor components, superconducting devices, SQUIDS, infrared components, optoelectronic devices, hybrid and monolithic integration, nanostructures and novel devices, processing, and modeling; 3) Circuits: integrated circuits, digital and analog circuits, charge-coupled devices and read-out circuits, low-temperature systems, design considerations, and superconducting circuits; 4) Systems: packaging, assembly and interconnections, reliability performance, low-to-room-temperature interfaces, heat transfer and refrigeration systems, and device and system testing; and 5) Applications: computer and telecommunications, space applications, infrared astronomy, instrumentation, low-temperature measurement systems. Abstract deadline, Nov. 1, 1996. Abstracts and inquiries should be sent to one of the symposium organizers: C. Claeys, IMEC, Kapeldreef 75, B-3001 Leuven, Belgium, telephone +32 16-281328, telefax +32 16-281214, e-mail claeys@imec.be; S. I. Raider, IBM Corporation, T. J. Watson Research Center, P. O. Box 218, Room 82-111, Yorktown Heights, NY 10598, telephone (914) 945-3822, telefax (914) 945-2018, e-mail raider@watson.ibm.com; M. J. Deen, School of Engineering, Simon Fraser University, Burnaby, B.C., Canada, V5A 1S6, telephone (604) 291-3248, telefax (604) 291-4951, e-mail jamal@cs.sfu.ca; W. D. Brown, Department of Electrical Engineering, University of Arkansas, 3220 Bell Engineering Center, Fayetteville, AR, telephone (501) 575-3009, telefax (501) 575-7967, e-mail wdb@engr.uark.edu; or R. K. Kirschman, P.O. Box 391716, Mountain View, CA 94039, telephone (415) 962-0200, telefax (415) 962-5763, e-mail randall@infoserv.com.
Information
New Book: Physical Properties of High Temperature Superconductors V, edited by Donald M. Ginsberg. Book has chapters of interest for both fundamental studies and applied research. Topics discussed include the electromagnetic response (penetration depth and surface resistance), local lattice distortions, the influence of vortex fluctuations on macroscopic behavior, the properties of superlattices, and the symmetry of the superconducting order parameter. Publ. 1996; 480 pp.; price $78; ISBN 981-02-2464-8. Contact World Scientific Publishing Co. Inc., 1060 Main St., River Edge, NJ 07661; telephone (800) 227-7562 or (201) 487-9655; telefax (201) 487-9656. In Europe, World Scientific Publishing Co. Ltd., 57 Shelton Street, Covent Garden, London WC2H 9HE, UK; telephone +44 171 836 0888; telefax +44 171 836 2020. In Asia, World Scientific Publishing Co. Pte. Ltd., Farrer Road, P.O. Box 128, Singapore 9128; telephone +65 3825663; telefax +65 3825919. Information also available at the web sites http://www.singnet.com.sg/~wspclib or http://www.wspc.co.uk.
Products and Services
Superconductive materials and kits for experimentation and demonstration of the fundamental properties of high-Tc superconductors are available from Colorado Superconductor, Inc. Available experiments range from basic demonstration of the Meissner effect to advanced exploration of critical parameters and superconductivity theory. Also available for individual sale are one-inch and half-inch diameter YBCO and BSCCO superconductor disks, flux-melted disks, and toroidal rings. Some other shapes also available. For more information or to place an order, contact Colorado Superconductor, Inc., P.O.Box 8223, Fort Collins, CO 80524; telephone (970) 490-2787; telefax (970) 490-1301; e-mail superconductors@csn.net. Information also available at the web site http://www.csn.net/superconductor.
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. 10, #16, August 15, 1996.