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, ONR, NSF, EPRI, and other agencies, organizations, and individuals.

The High-Tc Update web page is located at the URL http://www.iitap.iastate.edu/htcu/htcu.html

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:

d-Wave Evidence

An experiment by C. C. Tsuei (IBM-Yorktown) et al. [recently published in Nature 387, 481 (1997)] has found strong evidence for pure d_[x^2- y^2] order-parameter symmetry in the tetragonal, single-CuO2-layer superconductor Tl2Ba2CuO6+d (Tl-2201). The authors used a Tl-2201 film deposited on a (100) SrTiO3 substrate with a special bicrystal geometry chosen to perform a phase-sensitive test of pairing symmetry based only on symmetry considerations. As predicted theoretically by M. B. Walker and J. Luettmer-Strathmann [Phys. Rev. B 54, 598 (1996)] for such a junction between superconductors with d-wave pairing symmetry, a Josephson vortex carrying flux phi_0/2 (where phi_0 = h/2e is the usual superconducting flux quantum) was found at the bicrystal meeting point. A scanning SQUID microscope was used to map the magnetic field generated by the Josephson vortex.

A preprint by J. Orenstein (UC-Berkeley and LBNL) et al. describes two types of experiments in BSCCO films that probe the high-frequency conductivity in the presence of large superfluid velocities. In the first experiment (complex conductivity in the range 100-250 GHz in applied magnetic fields up to 7 T), the superflow is the static 1/r velocity field around each vortex axis. In the second, the superfluid velocity is dynamic, induced by high-intensity single-cycle (1 ps) electromagnetic pulses. The authors show that intrinsic pair breaking in a d-wave superconductor provides a unified explanation for both effects.

Vortices

The dynamics of vortices in d-wave superconductors have been studied by J. J. Vicente Alvarez et al. (Bariloche) using a phenomenological time- dependent Ginzburg-Landau equation with both s- and d-wave components. The authors present numerical simulations under an external driving current J oriented at an angle phi with respect to the b crystal axis, and calculate the vortex motion and induced electric fields for kappa = infinite. The authors find that the Hall angle varies as sin[4phi] and increases quadratically with J.

Using the Fokker-Planck equation, Y. Mawatari (ETL) has investigated the two-dimensional dynamics of vortices in planar pinning centers with thermal fluctuations, and has derived expressions for the electrical conductivity tensor sigma_[ij] and the resistivity tensor rho_[ij] due to vortex motion. The author finds that the off-diagonal components, sigma_[xy] and rho_[xy], have large contributions of symmetric parts, which do not change their signs upon reversal of the magnetic-field direction, due to the anisotropy of pinning and vortex viscosity. The symmetric part of the transverse resistivity, which is referred to as the even Hall effect, arises from competition between the guided motion of vortices in planar pinning centers and thermal hopping of vortices over the pinning barriers.

A theory of vortex dynamics treating the superfluid, the normal fluid, and the vortex system as three subsystems mutually connected by interactions has been developed by J. Kolacek (Prague) and E. Kawate (Tsukuba). The authors find that because of the finite range of the pinning force, nonlinear phenomena may be expected for some frequencies even for the relatively low driving fields commonly used experimentally.

The equilibrium dynamics of a thin-film type-II superconductor with spherical symmetry have been investigated numerically by A. K. Kienappel and M. A. Moore (Manchester) in simulations based on the lowest-Landau- level approximation to the time-dependent Ginzburg-Landau equation. In examining the behavior in the vortex-liquid phase, the authors found one main relaxation time scale in the decay of density correlations of the order parameter and in the self-diffusion of the vortices. They found no divergence of time scales or other features attributable to a phase transition at any finite temperature.

Noise measurements on untwinned single crystals of YBa2Cu3O7-d with columnar defects are reported by E. Shung (Chicago) et al. The authors used local Hall-probe magnetometry at mK temperatures to study the development of pinning in the strongly interacting Bose glass. The authors were able to resolve discrete fluctuations in the local vortex density (telegraph noise) resulting from reconfigurations of the vortex assembly between metastable states of nearly equal energy.

The Ginzburg-Landau model with a nonlocal quartic term has been studied by J. Yeo and M. A. Moore (Manchester) as a simple phenomenological model for superconductors in the presence of coupling between the vortex lattice and the underlying crystal lattice. In mean-field theory, this model is consistent with a general oblique vortex lattice ranging from a triangular lattice to a square lattice. The authors studied the effect of thermal fluctuations in the vortex-liquid regime, calculated the structure factor of the vortex liquid nonperturbatively, and found Bragg-like peaks with four-fold symmetry in the structure factor even though there is only short-range crystalline order.

The effects of interlayer defects in Bi2Sr2CaCu2O8+d (Bi-2212) single crystals have been studied by C. D. Keener et al. (Ohio State) using electrical transport measurements in crystals with varying amounts of disorder. The authors found that high-quality crystals consistently exhibit signatures of a first-order vortex-lattice melting transition and, at a higher temperature, a distinct vortex-line decoupling transition. Crystals with an intermediate amount of interlayer disorder can also exhibit signatures of a sharp vortex melting transition, but the interlayer coupling of vortex lines in the vortex solid is weakened by the disorder. In crystals of low quality and high disorder, continuous temperature dependence of the resistance and nearly ohmic transport properties suggest that a first-order vortex melting transition is absent.

A preprint by L. A. Angurel (Zaragoza) et al. reports the use of ac susceptibility measurements to determine the dimensionality of collective pinning in 2H-NbSe2 crystals. The authors found that down to thicknesses of 15 micrometers, the critical current density Jc(H) was independent of the thickness, indicating that the pinning is three- dimensional. Deviations were found to occur for a 6 micrometers sample near the peak-effect regime, possibly indicating a crossover to two- dimensional behavior.

The dynamics of curved vortex filaments have been studied analytically and numerically by I. S. Aranson (Bar Ilan and Argonne) and A. R. Bishop (Los Alamos) using a three-dimensional complex Ginzburg-Landau equation (CGLE). The authors find for a certain range of parameters of the CGLE that a straight vortex line is unstable with respect to spontaneous stretching and bending, resulting in the formation of persistent entangled vortex configurations.

A delocalization phenomenon has been studied by N. Hatano (Harvard and Tokyo) and D. R. Nelson (Harvard) in a class of non-Hermitian random quantum-mechanical problems. The transition is related to the depinning of flux lines from extended defects in type-II superconductors subjected to a tilted external magnetic field. The authors also determined the singular behavior of the penetration length describing stretched exponential screening of a perpendicular magnetic field (transverse Meissner effect), the surface transverse magnetization, and the trapping length near the flux-line-depinning point.

A preprint by E. B. Sonin (Helsinki University of Technology and St. Petersburg) reports an analysis of the plasma mode in layered superconductors using a continuous approach for an anisotropic superconductor and the Lawrence-Doniach model. The analysis predicts a magnetic-field dependence for the plasma frequency that differs from that of recently observed magnetoabsorption resonances. The author thus asserts that the interpretation of these resonances as Josephson-plasma- mode resonances is unlikely to be correct.

Theory

Pursuing the ideas of S.-C. Zhang [Science 275, 1089 (1997)], C. P. Burgess (McGill) and C. A. Luetkin (Oslo) set up effective field theories that describe the SO(5)-invariant picture of the high-Tc cuprates in various regimes. The authors use these to get quantitative conclusions concerning the size of SO(5)-breaking effects. The authors also identify which predictions depend on microscopic details of the underlying electron dynamics and which are model-independent.

A preprint by B. P. Stojkovic (Illinois-Urbana) and D. Pines (Los Alamos) presents a study of the normal-state optical conductivity in the cuprate superconductors using the nearly antiferromagnetic Fermi liquid (NAFL) description of the magnetic interaction between their planar quasiparticles. The authors state that the highly anisotropic scattering rate in different regions of the Brillouin zone, both as a function of frequency and temperature, a benchmark of NAFL theory, leads to an average relaxation rate having the marginal Fermi liquid (MFL) form for overdoped and optimally doped systems, as well as for underdoped systems at high temperatures.

A simple analytical model describing the normal state of a superconductor with a pseudogap in the density of states, such as in underdoped cuprates, is presented in a paper by O. Tchernyshyov (Columbia). The author obtains a pronounced suppression of the fermion density of states near zero energy, which makes room for long-lived pair states inside the gap. The fermion spectral weight exhibits two BCS- like peaks, broadened by fluctuations of the pairing field amplitude. At low momenta and frequencies, they represent a Bogoliubov sound-like mode with a nonzero mass.

According to B. Janko, J. Maly, and K. Levin (Chicago), resonant pair scattering of correlated electrons above Tc can give rise to pseudogap behavior. This resonance in the scattering T-matrix appears for superconducting interactions of intermediate strength within the framework of a simple fermionic model. It is associated with a splitting of the single peak in the spectral function into a pair of asymmetrically broadened peaks separated by an energy gap. The authors contrast their picture with other T-matrix schemes, with superconducting fluctuation effects, and with preformed pair (boson-fermion) models.

As shown by M. E. Zhitomirsky and M. B. Walker (Toronto), an induced s- wave harmonic in the superconducting gap of an orthorhombic d_[x^2-y^2] superconductor strongly affects the excitation spectrum near a twinning plane. In particular, it yields bound states of zero energy with areal density proportional to the relative weight of the s-wave component. The authors also identify an unusual scattering process responsible for the thermal conductivity across the twin boundary at low temperatures.

Twin boundaries in orthorhombic d-wave superconductors have been investigated numerically by D. L. Feder et al. (McMaster) using the Bogoliubov-de Gennes formalism within the context of an extended Hubbard model. The twin boundaries are represented by tetragonal regions of variable width, with a reduced chemical potential. For sufficiently large twin boundary width and change in chemical potential, an induced s-wave component may break time-reversal symmetry at a low temperature T*.

The two-dimensional Eliashberg equations have been solved by K. Sakai et al. (Science University of Tokyo) using a mixed interaction with s and d channels. The authors determine what kind of pairing symmetry of the superconducting state can be realized when the channel mixing parameters and the band filling are varied.

YBa2Cu3O7-d

A preprint by K. Watanabe (Tohoku) et al. reports the development of high-field and high-temperature heat-treatment equipment using an 11 T liquid helium-free superconducting magnet with a 52 mm diameter room temperature bore. The authors assert that this equipment has the potential for experiments in which a sample could be held in a 10 T field at temperatures up to 1200^oC for weeks or months. As a performance test, the authors developed a high-field seeding process for the growth of YBa2Cu3O7-d bulk materials at 10 T and 1000^oC for three days. The resulting material had improved crystallinity, sharper rocking curves, and a higher magnetically determined Jc.

The nucleation and growth of the orthorhombic phase by transformation through oxygen ordering from the tetragonal phase in melt-textured YBa2Cu3O7-d has been investigated by E. S. Reddy and T. Rajasekharan (Hyderabad) using polarized light microscopy. The authors found, for example, that the nucleation of the orthorhombic phase and the consequent formation of twins and lamellae occurred basically at three sites: high-angle domain boundaries, platelet boundaries, and macrocracks of thermomechanical origin.

Bi Cuprates

A letter by C. M. Lieber and P. Yang (Harvard) refers to a recent paper by I. Chong et al. [Science 276, 770 (1997); see also the preprint by I. Shimoyama (Tokyo) et al. listed in our June 1 issue] and points out that large, order-of-magnitude increases in Jc resulting from heavy Pb doping of Bi-2212 single crystals have been reported previously by Y. L. Wang et al. [Proc. Natl. Acad. Sci. USA 87, 7058 (1990)], and confirmed and extended by W. D. Wu et al. [Phys. Rev. B 47, 8172 (1993)].

A method for improving the strain tolerance of BPSCCO tapes by reinforcing the ceramic core with silver fibers has been developed by S. Salib and C. Vipulanandan (TCSUH). The addition of Ag fibers (15% by volume) improved the average irreversible strain of the composite tape to 0.3%, a 50% improvement over the monolithic tape.

As reported by Q. Li (Brookhaven) et al., the irreversibility field of c-axis-oriented superconducting Bi2Sr2Ca2Cu3O10+d (Bi-2223) tapes irradiated with 5.8 GeV Pb ions collapses at temperatures about 75% of Tc regardless of fluence. The authors suggest that this may indicate an ultimate limit for the field application of Bi-2223/Ag tapes at 77 K, since columnar defects produced by heavy ions are the most effective way known to optimize flux pinning in these materials.

The ac loss in multifilamentary Bi-2223/Ag tapes with twisted and non- twisted filaments has been studied by M. P. Oomen (Siemens) et al. using a magnetic method. By applying a dc transport current, the authors were able to distinguish between the loss components arising from intragranular and intergranular currents. The magnitude of the filament loss component indicates that the filaments are fully coupled, as expected theoretically. The authors assert that knowledge of the ac loss in parallel and perpendicular fields is sufficient to predict the ac loss for any intermediate orientations of the field.

The ac losses of Ag-sheathed Bi-2223 multifilamentary tapes at 77 K have been measured by M. Sugimoto (Furukawa Electric) et al. using a magnetization method. The ac losses of an untwisted tape were proportional to the frequency in a perpendicular ac field of amplitude 29 mT and were slightly lower below 70 Hz and larger above 150 Hz than those of a tape containing filaments with a twist pitch of 8.6 mm. The authors conclude that the coupling loss of untwisted HTS tapes is much smaller than the eddy-current loss at commercial frequencies because of complete electromagnetic coupling.

Other Cuprates

A nuclear magnetic resonance study of the Cu nuclei in the paramagnetic phase of Ca0.85Sr0.15CuO2, the antiferromagnetic parent compound of the infinite-layer superconductors, has been carried out by R. Pozzi (Zurich) et al. By measuring the temperature dependence of the magnetic and quadrupolar shift and of the spin-lattice relaxation rate, the authors found that with decreasing temperature, Ca0.85Sr0.15CuO2 undergoes two successive crossovers: a dimensionality crossover from a two-dimensional (2D) to a three-dimensional (3D) Heisenberg magnet followed, very close to T_N, by a spin-degree crossover from a 3D Heisenberg to a 3D XY antiferromagnet. The authors find no evidence for structural changes accompanying the magnetic phase transition.

A preprint by K. Isawa (Tohoku Electric Power) et al. reports the synthesis of delafossite-derived phases of RCuO2 (R = Y, La, Pr, Nd, Sm, and Eu). An oxygen-rich delafossite-derived phase, RCuO2+d (d >= 0.5), as previously reported by R. J. Cava et al. [J. Solid State Chem. 104, 437 (1993)] for R = Y and La, was found for all the other R presently studied. For Ca-doped YCuO2+d samples, an unusual temperature dependence of the magnetic susceptibility chi was found and analyzed using a model for two-leg Heisenberg ladders in the framework of S = 1/2 Heisenberg antiferromagnetism. A large value (Delta >= 600 K) was found for the spin gap.

The thermal conductivity kappa and thermoelectric power S of PrBa2Cu4O8 have been studied by M. Matsukawa (Iwate) et al. as a function of temperature. The results for both kappa and S support a dimensionality crossover of electronic transport from 1D conduction along the CuO chains to quasi-2D behavior, which results in band-like conduction along and between the CuO chains.

The HgBa2Ca2Cu3O8+d (Hg-1223) and HgBa2Ca3Cu4O10+d (Hg-1234) phases have been synthesized by K. A. Lokshin (Moscow State) et al. using a program- controlled high-pressure chamber. The authors found that variation of the oxygen content in the starting oxide mixture HgBa2Ca3Cu4Ox, obtained by changing the BaO/BaO2 and Cu2O/CuO ratios, significantly influenced the phase formation. An initial mixture with high oxygen content (x = 10.6) yielded strongly overdoped Hg-1223 with a Tc = 118 K, while subsequent treatment in oxygen flow enhanced Tc up to 134 K.

Borocarbides

The low-temperature specific heat of the superconductor LuNi2B2C has been measured by M. Nohara (Tokyo) et al. under various magnetic fields H up to 8 T. The coefficient gamma(H) of the T-linear term in the specific heat in the mixed state showed marked deviations from the H- linear dependence expected for conventional superconductors but was found to obey gamma(H) = gamma_N(H/H_[c2])^[1/2]. A good description of the data can be obtained by assuming the presence of a zero-gap region along lines on the Fermi surface, suggesting the possibility of unconventional pairing in the superconducting state in the borocarbides.

Thin Films

TBCCO thin films have been deposited on LaAlO3 substrates and SrTiO3 bicrystalline substrates by F. Schmidl (Jena) et al. using a sputtering technique followed by a post-annealing procedure. The films on the LaAlO3 substrates were patterned in such a way that the transport current measurements were carried out in the c direction, resulting in the observation of intrinsic Josephson effects. The authors also investigated the in-plane transport properties of grain-boundary Josephson junctions.

The effective activation energy U(J,H,T) extracted from the temperature dependence of the resistivity as a function of the current density and magnetic field up to 8T has been measured by Z. H. Wang et al. (Hefei) in an epitaxial YBa2Cu3O7-d thin film. Measurements of the field dependence for H||ab and H||c suggest a crossover of the vortex state from a quasi-2D liquid state for H||ab to a 3D line-liquid state for H||c.

Applications

A novel high-speed dc SQUID magnetometer with a planar integrated on- chip intermediary input transformer has been developed by V. Polushkin et al. (Oxford Instruments). The SQUID operates in an internal relaxation-oscillation mode. While the concept has been realized here in low-Tc SQUIDs, it also could be applied in high-Tc SQUIDs.

Three preprints by groups in Jena (two by P. Seidel et al. and one by L. Doerrer et al.) report advances in the fabrication of high-Tc SQUIDs and gradiometers for various applications. One of these papers reports on the development of a portable gradiometer system that works in an unshielded environment without additional field compensation. The authors demonstrate measurements of magnetocardiograms in a real clinical environment but note that the quality of the real-time traces is not sufficient for medical diagnosis.

The performance of a liquid-nitrogen-cooled semiconducting preamplifier coupled with high-Tc SQUIDs and SQUID gradiometers based on grain- boundary junctions is reported by N. N. Ukhansky (Troitsk) et al. This development offers the possibility of fabricating miniature magnetometer channels with low noise, determined by the SQUID itself, with high bandwidth and slew rate.

Other Activities

As reported by M. Houssa and M. Ausloos (Liege), the electronic contribution to the in-plane electronic thermal conductivity of high-Tc superconductors leads to a T^2 dependence of the electron-impurity contribution, not a T dependence.

The penetration of magnetic flux into type-II superconducting samples in the form of thin elliptic cylinders and circular disks is considered theoretically in a paper by K. V. Bhagwat (BARC-Bombay) and P. Chaddah (Indore). The authors obtain numerical solutions for the local field distribution and critical-state magnetization curves for two models incorporating the field dependence of Jc.

A procedure for obtaining the ideal reversible magnetization curve from low-frequency measurements of the ac magnetic permeability in low- pinning samples such as Pb1-xInx slabs is reported by H. Vasseur et al. (ENS-Paris).

The dynamics of current-biased Josephson-junction arrays with magnetic penetration depth lambda_[perp.] smaller than the lattice spacing has been studied experimentally and theoretically by S. G. Lachenmann (Tuebingen) et al. The authors compare the dynamics imaged by low- temperature scanning electron microscopy in Nb/AlOx/Nb junction arrays to the vortex dynamics obtained from model calculations based on the resistively shunted junction model.

The ac magnetic susceptibility of the high-field C phase of UPt3 has been measured by B. Ellman and L. Taillefer (McGill). The authors interpret the results in terms of vortex pinning, which while comparatively small in the A and B phases, becomes large enough to effectively prevent vortex motion in the C phase.

Overviews

A review of advances in the state of the art of high-temperature superconductivity (HTS) mainly in the period from the end of 1994 to the beginning of 1996 has been prepared by S. X. Dou (Wollongong) et al. Topics include discoveries of new HTS compounds, the preparation of single crystals, chemical properties, theory, and improvement of flux pinning (289 refs.).

Various experimental results on the preparation of high-Tc Hg-based cuprate thin films and their fabrication into rf and dc superconducting quantum interference devices (SQUIDs) have been reviewed by N. Khare (NPL-New Delhi) et al. SQUID behavior in such devices has been observed at temperatures around 110 K (38 refs.).

An overview by J. Orenstein et al. (UC-Berkeley and LBNL) discusses the high-frequency (100-1000 GHz) electrodynamics of cuprate superconductors in the vortex state. The authors stress that in this frequency range, vortex dynamics models commonly used to explain the low-frequency data do not apply. Instead, a model accounting for the large change in the d-wave quasiparticle density of states (QPDOS) due to the presence of vortices can successfully explain the data (32 refs.).

A review of the contributions that high-pressure studies have made towards current understanding of the alkali-doped fullerides such as K3C60 and Rb3C60 has been written by J. S. Schilling et al. (Washington University). While these materials have a negative pressure derivative dTc/dP, as do the elemental superconductors Al, Sn, and Pb, the physical origin of this effect is entirely different in the two classes of materials (31 refs.).

Contributed by John R. Clem

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.

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 space-qualified experiment to test the performance of HTSC in space was delivered to the Asher Space Institute at Technion for integration in the TECHSAT satellite. The TECHSAT, a miniature satellite designed around the concept of providing a small inexpensive platform for testing new technologies, is scheduled to be launched in September 1997. It weighs only 48 kg and its total power budget is 25 W out of which housekeeping tasks by the control systems require 10 W, leaving 15W for all the experiments on board. The HTSC experiment, designed and built at the Technion Physics Department, consists of a thin YBCO film on an MgO substrate patterned into a microbridge that is mounted on a miniature cryocooler manufactured by RICOR (Israel). A dedicated electronics package measures the R-T curve during cooldown and the critical current, I_c vs. temperature below Tc. The experiment weighs about 500 gm and consumes about 13 W. In orbit, the cooler will be turned on for a specified period of time and the R-T and I_c-T curves will be recorded during cooldown. Variations of these properties with time will test the longevity and robustness of HTSC in space, an input needed to move the satellite communication applications forward. For information, contact Emil Polturak, Department of Physics, Technion, Haifa 32000, Israel; telephone +972 4829-2761; telefax +972 4822-1514; e-mai emilp@physics.technion.ac.il.

A superconducting magnet cable composed of 50 BSSCO/Ag silver-sheathed tapes has been fabricated by Europa Metalli (Florence, Italy), using tapes produced by American Superconductor Corp. Ten meters of the magnet cable have been wound onto a solenoid and tested down to liquid He temperatures. At liquid N2 temperatures, the cable is capable of transporting currents up to 1000 A, and at liquid He temperatures the cable has transported 4000 A generating a field of 1 T. The aim of the project is to demonstrate the possibility of using these conductors in the fields of high-energy physics and controlled thermonuclear fusion. For further information, contact American Superconductor Corporation, Two Technology Drive, Westborough, MA 01581; telephone (508) 836-4200; telefax (508) 836-4248.

Contributed by Sreeparna Mitra

J. J. Vicente Alvarez, D. Dominguez, and C. A. Balseiro, "Dynamics of d- Wave Vortices: Angle-Dependent Nonlinear Hall Effect." Submitted to Phys. Rev. Lett. Centro Atomico Bariloche, 8400 S. C. de Bariloche, Rio Negro, ARGENTINA; D. Dominguez's e-mail domingd@cab.cnea.edu.ar; preprint also available at cond-mat@xxx.lanl.gov (#9704188). 74.60.Ge; 74.20.De; 74.25.Fy.

L. A. Angurel, F. Amin, M. Polichetti, J. Aarts, and P. H. Kes, "Dimensionality of Collective Pinning in 2H-NbSe2 Single Crystals." To be published in Phys. Rev. B. I.C.M.A., Departamento de Ciencia y Tecnologia de Materiales y Fluidos, Centro Politecnico Superior, Universidad de Zaragoza, Maria de Luna 3, E-50015 Zaragoza, SPAIN; telephone +34 976-761958 or -761000 ext 5140; telefax +34 976-761957; e- mail luis_a_angurel@mcps.unizar.es. 74.60.Ge; 74.60.Jg.

I. Aranson and A. R. Bishop, "Stretching of Vortex Lines and Generation of Vorticity in the Three-Dimensional Complex Ginzburg-Landau Equation." Submitted to Phys. Rev. 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. 05.45.+b; 47.20.Ky; 47.27.Eq.

V. S. Barashenkov, I. N. Goncharov, B. F. Kostenko, and V. P. Filinova, "Computation of Thermal Relaxation of Energy in High Tc Superconductor YBCO." Preprint #P17-96-511. Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, RUSSIA.

K. V. Bhagwat and P. Chaddah, "Flux Penetration in Thin Superconductor Films with Field Dependent Critical Current Density." To be published in Physica C (in press). Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Center, Mumbai 400 085, INDIA; telefax +91 22 556 O750; e-mail sspd@magnum.barctl.ernet.in.

C. P. Burgess and C. A. Luetken, "SO(5) Invariance and Effective Field Theory for High-Tc Superconductors." Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, CANADA H3A 2T8; e- mail cliff@physics.mcgill.ca; preprint also available at cond- mat@xxx.lanl.gov (#9705216).

L. Doerrer, S. Wunderlich, F. Schmidl, H. Schneidewind, P. Seidel, and U. Huebner, "Development of Planar Thin Film HTSC-SQUID Gradiometers for Different Applications." Submitted to the 6th Int. Supercond. Electronics Conf. (ISEC'97), Berlin, Germany, June 26 - 28, 1997. Institut fuer Festkoerperphysik, Freidrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena, GERMANY; P. Seidel's telephone +49 3641- 635685 or -635681; telefax +49 3641-635681; e-mail seidel@ifk.uni- jena.de.

S. X. Dou, P. N. Mikheenko, X. L. Wang, and H. K. Liu, "High-Temperature Superconductors." To be published in Royal Soc. of Chem. -- Annual Reports, Book C. Centre for Superconducting & Electronic Materials, Institute of Materials Technology and Manufacturing, University of Wollongong, Wollongong , NSW 2522, AUSTRALIA.

Brett Ellman, Mark Sutton, Benoit Lussier, Ralf Bruening, Louis Taillefer, Stephen Hayden, and Grace Shea-McCarthy, "Search for Structural Modulations in UPt3 Using Laue X-ray Diffraction." Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, CANADA H3A 2T8; e-mail brett@physics.mcgill.ca; preprint also available at cond-mat@xxx.lanl.gov (#9704125). 74.25.Ld; 74.70.Tx.

Brett Ellman and Louis Taillefer, "Intrinsic Pinning in the High Field c-Phase of UPt3." Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, CANADA H3A 2T8; e-mail brett@physics.mcgill.ca; preprint also available at cond- mat@xxx.lanl.gov (#9705078).

D. L. Feder, A. Beardsall, A. J. Berlinsky, and C. Kallin, "Twin Boundaries in d-Wave Superconductors." Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, CANADA L8S 4M1; e- mail feder@ivy.physics.mcmaster.ca; preprint also available at cond- mat@xxx.lanl.gov (#9705139). 61.72.Mm; 74.20.-z; 74.50.+r; 74.72.Bk.

R. Friedberg, H. C. Ren, and O. Tchernyshyov, "Comment on the 'Boson- Fermion Model Beyond the Mean-Field Approximation.'" Submitted to J. Phys. Cond. Mat. Department of Physics, Columbia University, New York, NY 10027; O. Tchernyshyov's e-mail olegt@cuphyb.phys.columbia.edu; preprint also available at cond-mat@xxx.lanl.gov (#9705089). 74.20.Mn; 11.25.Db.

A. Gencer, A. Ates, E. Aksu, S. Nezir, S. Celebi, and E. Yanmaz, "Microstructural and Physical Properties of YBa2Cu3O7-d Superconductors Prepared by the Flame-Quench-Melt Growth (FQMG) Method." To be published in Physica C (in press). Department of Physics, Faculty of Sciences, Ankara University, 06100 Tandogan, Ankara, TURKEY; telephone +90 312 212 6720 ext. 1161; telefax +90 312 223 2395; e-mail gencer@science.ankara.edu.tr. Key words: ac susceptibility, critical current density, microstructure and YBCO materials preparation.

Naomichi Hatano and David R. Nelson, "Vortex Pinning and Non-Hermitian Quantum Mechanics." Lyman Laboratory of Physics, Harvard University, Cambridge, MA 02138. 72.15.Rn; 74.60.Ge; 05.30.Jp.

M. Houssa and M. Ausloos, "Comment on 'Electronic Thermal Conductivity and the Wiedemann-Franz Law for Unconventional Superconductors.'" To be published in Phys. Rev. B. S.U.P.R.A.S., Institut de Physique B5, Universite de Liege, B-4000 Liege, BELGIUM; telephone +32 41 66 3703; telefax +32 41 66 2990; M. Ausloos' e-mail ausloos@gw.unipc.ulg.ac.be; Web site http://www.phe.ulg.ac.be/.

M. N. Iliev. H.-U. Habermeier, M. Cardona, V. G. Hadjiev, and R. Gajic, "Transformations of the Local Structure of YBa2Cu3O7-d Due to Laser Annealing." To be published in Physica C (in press). Contact V. G. Hadjiev, Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY. Key words: Raman scattering, oxygen stoichiometry, phonon spectrum, Cu-O chains, defect structures.

Kazuyuki Isawa, Yuji Yaegashi, Motoharu Komatsu, Mitsugu Nagano, Shiroshi Sudo, Maarit Karppinen, and Hisao Yamauchi, "Synthesis of Delafossite-Derived Phases, RECuO2+d with RE=Y,La,Pr,Nd,Sm and Eu, and Observation of Spin Gap-Like Behavior." 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; e-mail kazu@rdc.tohoku-epco.co.jp. 72.20.-i; 74.10.+v; 75.20.Hr.

Boldizsar Janko, Jiri Maly, and K. Levin, "Pseudogap Effects Induced by Resonant Pair Scattering." James Franck Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637; telephone (773) 702-0609; telefax (773) 702 5863; e-mail janko@rainbow.uchicago.edu; preprint also available at cond-mat@xxx.lanl.gov (#9705144). 74.20.Mn; 74.25.-q; 74.25.Fy; 74.25.Nf; 74.72.-h.

Z. M. Ji, J. F. Geng, W. M. Chen, H. X. Yu, A. M. Sun, Q. H. Chen, S. Z. Yang, and X. Jin, "Magnetization Hysteresis Loops of the Granular High- Tc Superconductors in the ac Measurements." To be published in Physica C (in press). Contact X. Jin, Department of Physics and National Laboratory of Solid State Microstructure, Nanjing University, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA; telefax +86 25 360 9458; e-mail postphys@nju.edu.cn.

C. D. Keener, S. M. Ammirata, M. L. Trawick, and J. C. Garland, "Effect of Interlayer Disorder on Vortex Melting in Bi2Sr2CaCu2O8+d Crystals." Submitted to Physica C. Contact S. M. Ammirata, Department of Physics, Ohio State University, 174 W. 18th Avenue, Columbus, OH 43210-1106; telephone (614) 292-5713; e-mail ammirata@mps.ohio-state.edu. Key words: flux flow, defect structures, electrical resistivity, phase diagram, flux lattice.

Neeraj Khare, A. K. Gupta, Sangeeta Khare, H. K. Singh, and O. N. Srivastava, "Hg-Ba-Ca-Cu-O High-Tc Thin Films and Superconducting Quantum Interference Devices." To be published in Studies of High Temp. Supercond., Vol. 25, edited by A. V. Narlikar (Nova Science Publishers Inc., New York). 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.

A. K. Kienappel and M. A. Moore, "Numerical Investigation of the Dynamics of a Thin Film Type II Superconductor with and without Disorder." Submitted to Phys. Rev. B. Department of Physics, Theory Group, University of Manchester, Manchester M13 9PL, UNITED KINGDOM; e- mail anne@a13.ph.man.ac.uk; preprint also available at cond- mat@xxx.lanl.gov (#9705151). 74.20.De; 74.60.Ge; 74.76.-w.

G. C. Kim and Y. C. Kim, "Magnetic Field and Temperature Dependence of the Intergranular Activation Energy in a Polycrystalline HgBa2Ca2Cu3O8+d Superconductor." To be published in Physica C (in press). Contact Y. C. Kim, Department of Physics, Pusan National University, Pusan 609-735, SOUTH KOREA. Key words: ac susceptibility, high-Tc superconductors, activation energy.

G. C. Kim and Y. C. Kim, "Magnetic Relaxations of the Grain-Aligned Tl0.5Pb0.5Sr2Ca2Cu3Oy Superconductor." To be published in Physica C (in press). Contact Y. C. Kim, Department of Physics, Pusan National University, Pusan 609-735, SOUTH KOREA. Key words: magnetic relaxation, collective pinning model, effective activation energy, flux bundle.

Jan Kolacek and Etsuo Kawate, "High Frequency Vortex Dynamics and Magnetoconductivity of High Temperature Superconductors." Submitted to Phys. Rev. B. Institute of Physics, ASCR, Cukrovarnicka 10, 16200 Prague 6, CZECH REPUBLIC; telephone +42 2 243 11137; telefax +42 2 312 3184; e-mail kolacek@fzu.cz. 74.60.Ge; 74.25.Fy.

R. Krupke, G. Ulmer, R. Schneider, M. Kurzmeier, G. Linker, and J. Geerk, "Superconducting, Structural and Surface Properties of GdBaCuO Thin Films Deposited by Electron Cyclotron Resonance Supported Sputtering." To be published in Physica C (in press). Contact G. Linker, Forschungszentrum Karlsruhe, Institut fuer Nukleare Festkoerperphysik, Postfach 3640, D-76021 Karlsruhe, GERMANY; telephone +49 7247 823980; telefax +49 7247 824624; e-mail linker@infp.fzk.de. Key words: thin films, ECR sputter deposition, phase diagram, defect structures.

S. G. Lachenmann, T. Doderer, R. P. Huebener, T. J. Hagenaars, J. E. van Himbergen, P.H.E. Tiesinga, and Jorge V. Jose, "Current-Induced Vortex Dynamics in Josephson-Junction Arrays: Imaging Experiments and Model Simulations." To be published in Phys. Rev. B. Institut fuer Schicht- und Ionentechnik, Forschungszentrum Juelich, D-52425 Juelich, GERMANY; T. J. Hagenaars e-mail in Wuerzburg, Germany hagenaar@physik.uni- wuerzburg.de; preprint also available at cond-mat@xxx.lanl.gov (#9705194). 74.50.+r; 74.60.Ge.

A. Leenders, M. Ullrich, and H. C. Freyhardt, "Influence of Thermal Cycling on the Mechanical Properties of VGF Melt-Textured YBCO." To be published in Physica C (in press). Institut fuer Metallphysik, Universitaet Goettingen, Hospitalstrasse 3-7, D-37073 Goettingen, GERMANY; telephone +49 551 507 1730; telefax +49 551 507 1750; e-mail leenders@umpsunl.gwdg.de. Key words: mechanical properties, YBCO, thermal cycling. 62.20.Mk; 74.72.Bk; 74.25.Ld.

J. B. le Grand, M. P. Bruijn, C. Patel, P.A.J. de Korte, S. Lemke, R. Gross, and R. P. Huebener, "Low Temperature Scanning Electron Microscope Measurements on a Nb/Ta Junction." To be published in Physica C (in press). Contact P.A.J. de Korte, Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, THE NETHERLANDS; e-mail p.de.korte@sron.ruu.nl.

Qiang Li, M. Suenaga, T. Kaneko, K. Sato, and Ch. Simmon, "Collapse of Irreversible Field of Superconducting Bi2Sr2Ca2Cu3O10+d/Ag Tapes with Columnar Defects." Department of Applied Sciences, Brookhaven National Laboratory, Upton, NY 11973.

Xiao-Guang Li, Xuefeng Sun, Wenbin Wu, Qianwang Chen, Lei Shi, Yuheng Zhang, Y. Kotaka, and K. Kishio, "Variations of Normal State Resistivity and Cu^[2+] Localized Spin Moment in the Single Crystal Bi2Sr2CaCu2O8+x." To be published in Physica C (in press). Structure Research Laboratory, University of Science and Technology of China, Hefei 230026, PEOPLE'S REPUBLIC OF CHINA. Key words: Bi2Sr2CaCu2O8+x, electron spin resonance, resistivity, localized spin moment.

Charles M. Lieber and Peidong Yang, "Letter to the Editor," submitted to Science. Harvard University, 12 Oxford Street, Cambridge, MA 02138; telephone (617) 496-3169; telefax (617) 496-5442 or -6731; e-mail cml@cmliris.harvard.edu.

K. A. Lokshin, I. G. Kuzemskaya, L. F. Kulikova, E. V. Antipov, and E. S. Itskevich, "High Pressure Synthesis of Hg-1234 and Strongly-Overdoped Hg-1223 Phases." To be published in Physica C (in press). Contact E. S. Itskevich, Institute of High Pressure Physics RAS, 142092 Troitsk, Moscow Region, RUSSIA; telefax +7 095 334 0589; e-mail itskev@ns.hppi.troitsk.ru. Key words: high-pressure synthesis, Hg- 1223, Hg-1234, superconductivity in overdoped region.

*Jing Lu, Xiaobin Feng, Liyuan Zhang, and Yun Liu, "Determination of the Mixing Potential V Between the Bipolaron and the Itinerant Electron and Possible Two-Component Interaction Superconductivity Based on a Low N(E_F) for Doped Fullerenes." To be published in Physica C (in press). Department of Physics, 32+13 Peking University, Beijing 100871, PEOPLE'S REPUBLIC OF CHINA. Key words: Anderson lattice, bipolaronic superconductivity, electronic structure. 71.20.-b; 71.38.+i; 74.20.-z. *Revised manuscript.

L. P. Ma, H. C. Li, R. L. Wang, and L. Li, "The Nature of the Relaxation of Resistivity in High-Tc Superconductors." To be published in Physica C (in press). Beijing Laboratory of Vacuum Physics, Chinese Academy of Sciences, P. O. Box 2724, Beijing 100080, PEOPLE'S REPUBLIC OF CHINA. Key words: relaxation, resistivity, flux creep, high-Tc superconductor.

Michiaki Matsukawa, Kimiaki Iwasaki, Koshichi Noto, Yuh Yamada, and Shigeru Horii, "Thermal Transport of Metallic PrBa2Cu4O8 Compound Prepared by High-Oxygen-Pressure Method." To be published in Jpn. J. Appl. Phys. Department of Materials Science and Technology, Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020, JAPAN; telephone +81 19 621 6358; telefax +81 19 621 6373; e-mail matsukawa@msv.cc.iwate- u.ac.jp. Key words: PrBa2Cu4O8 compound, thermal conductivity, thermoelectric power, double CuO chains, dimensional crossover.

Yasunori Mawatari, "Dynamics of Vortices in Planar Pinning Centers and Anisotropic Conductivity in Type-II Superconductors." To be published in Phys. Rev. B. Frontier Technology Division, Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305, JAPAN; telephone +81 298 58 5737; telefax +81 298 58 5726; e-mail mawatari@etl.go.jp. 74.60.Ge; 74.40.+k; 72.15.Gd; 05.40.+j.

H. Miao, J. C. Diez, L. A. Angurel, J. I. Pena, and G. F. de la Fuente, "Phase Formation and Microstructure of Laser Float Zone Grown BSCCO Fibers: Reactivity Aspects." To be published in Solid State Ionics. Contact G. F. de la Fuente, Instituto de Ciencia de Materials de Aragon, CSIC-Universidad de Zaragoza, c/Maria de Luna 3, E-50015 Zaragoza, SPAIN; telefax +34 76 761957; e-mail xerman@posta.unizar.es. Key words: BSCCO superconductors, reactivity, directional solidification, texture.

V. A. Moskalenko, D. F. Digor, L. A. Dogotaru, and I. G. Porcescu, "New Diagram Technique for Periodic Anderson Model." Preprint #E17-96-465; submitted to J. Supercond. Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, RUSSIA; telefax +7 095 975 23 81.

V. A. Moskalenko, L. A. Dogotaru, and I. G. Porcescu, "Electron-Phonon Coupling for the System with Strong Electron Correlations." Preprint #E17-96-464; submitted to TM[Phi] Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, RUSSIA; telefax +7 095 975 23 81.

Minoru Nohara, Masanobu Isshiki, Hidenori Takagi, and R. J. Cava, "Magnetic Field Dependence of the Low-Temperature Specific Heat of the Borocarbide Superconductor LuNi2B2C." To be published in J. Phys. Soc. Jpn. 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 nohara@troy.issp.u-tokyo.ac.jp. Key words: borocarbide superconductors, LuNi2B2C, specific heat, quasiparticle states.

M. P. Oomen, J. Rieger, M. Leghissa, and H.H.J. ten Kate, "Magnetic ac loss in Multifilamentary Bi-2223/Ag Tapes." Submitted to Physica C. Siemens AG, Corporate Technology, Postfach 3220, D-91050 Erlangen, GERMANY; M. Leghissa's telephone +49 9131 7 32634; telefax +49 9131 7 33323; e-mail martino.leghissa@erls.siemens.de. Key words: ac loss, magnetization, grain boundaries. 74.25.Ha; 74.60.-w.

J. Orenstein, J. Bokor, E. Budiarto, J. Corson, R. Mallozzi, I. Bozovic, and J. N. Eckstein, "Nonlinear Electrodynamics in Cuprate Superconductors." To be published in Physica C: Proc. of the 5th Int. Conf. on Mater. and Mech. of Supercond. -- High-Temp. Supercond. (M^2S- HTSC V), Beijing, People's Republic of China, Feb. 28-Mar. 4, 1997. University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA 94720.

J. Orenstein, R. P. Mallozzi, and Beth Parks, "High-Frequency Electrodynamics of Cuprate Superconductors in the Vortex State." To be published in Supercond. in a Magnetic Field, edited by Carlos Sa de Melo (World Scientific). University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley, CA 94720.

Xavier Oudet, "Conductivity, Superconductivity and Defects." English version of "Conductivite, Supraconductivite et Defauts" to be published in Annales de la Fondation Louis de Broglie 1997. Laboratoire de Magnetisme et d'Optique, Batiment Fermat, Universite de Versailles, C.N.R.S., 45 Avenue des Etats-Unis, F-78035 Versailles Cedex, FRANCE; telephone +33 1 39 25 46 54; e-mail xavier.oudet@physique.uvsq.fr.

S. S. Perry, H. I. Kim, and P. B. Merrill, "Generation of Atomically Flat Magnesium Oxide Surfaces: Influence of Ambient Gas Composition During High Temperature Anneals." Preprint #97:047; submitted to Surface Science. Department of Chemistry, University of Houston, Houston, TX 77204-5641; telephone (713) 743-2715; e-mail perry@jestons.uh.edu. Key words: magnesium oxide, surface roughness and topography, atomic force microscopy, etching, annealing, surface reconstruction.

V. Polushkin, D. Glowacka, and John M. Lumley, "dc SQUID with an Intermediary Transformer Operating in an Internal Relaxation Oscillation Mode." Oxford Instruments, Scientific Research Division, Newton House, Cambridge Business Park, Cowley Road, Cambridge CB4 4WZ, UNITED KINGDOM; telephone +44 1223 427400; telefax +44 1223 425050; e-mail vladimir.polushkin@oxinst.co.uk; Web site http://www.oxinst.com/.

R. Pozzi, M. Mali, M. Matsumura, F. Raffa, J. Roos, and D. Brinkmann, "Paramagnetic Phase of the Infinite-Layer Antiferromagnet Ca0.85Sr0.15CuO2 as Seen by Cu NMR." To be published in Phys. Rev. B. Physik-Institut, Universitaet Zurich, CH-8057 Zurich, SWITZERLAND. 76.60.-k; 74.72.Jt; 75.50.Ee; 75.40.Gb.

E. Sudhakar Reddy and T. Rajasekharan, "Nucleation and Growth of the Orthorhombic Phase in Melt Textured YBa2Cu3O6+d." To be published in Physica C (in press). Defence Metallurgical Research Laboratory, P.O. Kanchanbagh, Hyderabad 500 258, INDIA. Key words: O-T transition, twins, oxidation process, YBa2Cu3O6+d.

S. B. Roy and P. Chaddah, "Study of Minor Hysteresis Loops in the Usual and Anomalous Superconducting Regime of (Ce0.95Nd0.05)Ru2: Evidence of a First-Order Transition." To be published in Physica C (in press). Low Temperature Physics Group, Centre for Advanced Technology, Indore 452013, INDIA.

Sascha Sadewasser, Craig Looney, James S. Schilling, John A. Schlueter, Jack M. Williams, Paul G. Nixon, Rolf W. Winter, and Gary L. Gard, "Dependence of Tc on Hydrostatic Pressure in Beta"-(ET)2SF5CH2CF2SO3 and kappa-(ET)2Cu(NCS)2." Submitted to Phys. Rev. B. Department of Physics, Washington University, C.B. 1105, One Brookings Dr., St. Louis, MO 63130-4899.

Katsuji Sakai, Yasushi Yokoya, and Yoshiko Oi Nakamura, "Phase Diagram of the Pairing Symmetry in Two-Dimensional Strong-Coupling Superconductors." To be published in Physica C (in press). Department of Applied Physics, Faculty of Science, Science University of Tokyo, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162, JAPAN; telephone +81 3 3260 4271, ext. 2425; telefax +81 3 3260 4772; e-mail sakai@grad.ap.kagu.sut.ac.jp. Key words: two-dimensional strong-coupling superconductor; pairing symmetry, mixed interaction of s- and d-wave, band filling, high Tc .

S. Salib and C. Vipulanandan, "Tensile Stress-Strain-Critical Current Relationships for Silver Fiber Reinforced BPSCCO Composite Tapes." Preprint #97:046; to be published in Mater. Res. Bull. 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: superconductors, metals, ceramics, x-ray diffraction, mechanical properties.

Sujit Sarkar, "Isotope-Shift Exponent and the Gap Ratio Within the Extended Saddle Point Singularity Scenario for Different Pairing Symmetries." To be published in Physica C (in press). Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064, INDIA; telephone +91 337 534549; telefax +91 33 3374637; e-mail atin@hpl.saha.ernet.in. Key words: BCS model, pairing symmetries, extended saddle-point singularity, isotope effect and gap ratio. 74.20.-z; 74.20.Fg; 74.62.- c; 74.62.Dh.

James S. Schilling, Jost Diederichs, and Anup K. Gangopadhyay, "High Pressure Studies on Fullerene Superconductors." To be published in Fullerenes: Recent Advances in the Chem. and Phys. of Fullerenes and Related Materials, Vol. IV, edited by K. M. Kadish and R. S. Ruoff (Pennington: Electrochem. Soc.). Department of Physics, Washington University, C.B. 1105, One Brookings Dr., St. Louis, MO 63130.

F. Schmidl, A. Pfuch, S. Wunderlich, P. Seidel, U. Huebner, and M. Veith, "In-Plane and Out-of-Plane Transport Measurements in TBCCO Josephson Junctions." Submitted to the 6th Int. Supercond. Electronics Conf. (ISEC'97), Berlin, Germany, June 26 - 28, 1997. Institut fuer Festkoerperphysik, Freidrich-Schiller-Universitaet Jena, Lessingstrasse 8, D-07743 Jena, GERMANY; P. Seidel's telephone +49 3641-635685 or -635681; telefax +49 3641-635681; e-mail seidel@ifk.uni-jena.de.

Paul Seidel, Sven Linzen, and Frank Schmidl, "High-Tc Thin Films and Josephson Junctions on Silicon and Sapphire Substrates." Submitted to the 5th Int. Workshop on High-Temp. Supercond. Electron Devices (HTSED'97), Matsuyama, Japan, May 28-30, 1997. Institut fuer Festkoerperphysik, Freidrich-Schiller-Universitaet Jena, Lessingstrasse 8, D-07743 Jena, GERMANY; telephone +49 3641-635685 or -635681; telefax +49 3641-635681; e-mail seidel@ifk.uni-jena.de.

P. Seidel, R. Weidl, S. Brabetz, F. Schmidl, H. Nowak, and U. Leder, "Magnetocardiography with High-Tc Gradiometers Working in Unshielded Environment." Submitted to the 6th Int. Supercond. Electronics Conf. (ISEC'97), Berlin, Germany, June 26 - 28, 1997. Institut fuer Festkoerperphysik, Freidrich-Schiller-Universitaet Jena, Lessingstrasse 8, D-07743 Jena, GERMANY; telephone +49 3641-635685 or -635681; telefax +49 3641-635681; e-mail seidel@ifk.uni-jena.de.

E. Shung, T. F. Rosenbaum, S. N. Coppersmith, G. W. Crabtree, and W. Kwok, "Vortex Telegraph Noise in High Magnetic Fields." Submitted to Phys. Rev. Lett. The James Franck Institute and Department of Physics, University of Chicago, Chicago, IL 60637; 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. 74.72.Bk; 74.60.Ge; 05.40.+j.

E. B. Sonin, "Has Josephson-Plasma Mode Been Observed in Layered Superconductors?" Submitted to Phys. Rev. Lett. Ioffe Physical Technical Institute, St. Petersburg 194021, RUSSIA; e-mail sonin@pk.pti.spb.su. 72.30.+q; 74.60.Ec; 74.60.Ge.

Branko P. Stojkovic and David Pines, "Theory of the Optical Conductivity in the Cuprate Superconductors." Department of Physics and Materials Research Laboratory, 1110 West Green Street, University of Illinois, Urbana, IL 61801; telephone (217) 244-6242 or (217) 333-0115; telefax (217) 244-7559; e-mail branko@uiuc.edu.

Masahiro Sugimoto, Akio Kimura, Masanao Mimura, Yasuzo Tanaka, Hideo Ishii, Shoichi Honjo, and Yoshihiro Iwata, "Electromagnetic Interfilament Coupling of Silver-Sheathed Bi-2223 Multifilamentary Tapes in Transverse ac Magnetic Fields." To be published in Physica C (in press). Furukawa Electric Co., Ltd., 500 Kiyotaki-machi, Nikko, Tochigi 321-14, JAPAN.

Xuefeng Sun, Wenbin Wu, Xiaoru Zhao, Lei Zheng, Guien Zhou, Xiao-Guang Li, and Yuheng Zhang, "Phase Decomposition and Oxygen Diffusion of Bi2Sr2CaCu2Oy Single Crystals Annealed in Various Atmospheres." To be published in Physica C (in press). Structure Research Laboratory, University of Science and Technology of China, Academia Sinica, Hefei 230026, PEOPLE'S REPUBLIC OF CHINA.

Ajay Mohan Suvarna, and C. S. Sunandana, "Estimation of Magnetic Penetration Depth in Li-Doped Polycrystalline Bi-2212: An ESR Study." To be published in Physica C (in press). Contact C. S. Sunandana, School of Physics, University of Hyderabad, Hyderabad 500 046, INDIA; telephone +91 40 258500; telefax +91 40 258120; e-mail csssp@uohyd.ernet.in.

Oleg Tchernyshyov, "Non-Interacting Cooper Pairs Inside a Pseudogap." To be published in Phys. Rev. B. Department of Physics, Columbia University, New York, NY 10027; e-mail olegt@cuphyb.phys.columbia.edu; preprint also available at cond-mat@xxx.lanl.gov (#9705124).

C. C. Tsuei, J. R. Kirtley, Z. F. Ren, J. H. Wang, H. Raffy, and Z. Z. Li, "Pure d_[x^2-y^2] Order Parameter Symmetry in the Tetragonal Superconductor Tl2Ba2CuO6+d." To be published in Nature (in press). IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598.

Nikolay N. Ukhansky, Sergey A. Gudoshnikov, Roland Weidl, Lars Doerrer, and Paul Seidel, "A Liquid-Nitrogen-Cooled Preamplifier in Connection with a High-Tc SQUID: Direct Readout and Flux-Locked Loop with ac Bias." Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, RAS, Troitsk, Moscow Region 142092, RUSSIA; P. Seidel's telephone at Jena, Germany, +49 3641-635685 or -635681; telefax +49 3641-635681; e-mail seidel@ifk.uni-jena.de.

H. Vasseur, P. Mathieu, B. Placais, and Y. Simon, "Observation of the Ideal Low-Frequency Response of the Mixed State and the Diamagnetism of a Type II Superconductor." To be published in Physica C (in press). Contact Y. Simon, Laboratoire de Physique de la Matiere Condensee de l'Ecole Normale Superieure, CNRS URA 1437, F-75231 Paris Cedex 05, FRANCE; telephone +33 1 4432 3507; telefax +33 1 4432 3840; e-mail ysimon@physique.ens.fr. Key words: mixed state, magnetization, ac susceptibility, flux flow, lower-critical-field H_[c1].

Z. H. Wang, K. B. Li, J. Fang, J. L. Chen, and X. W. Cao, "The Effective Activation Energy U(J,H) in Epitaxial YBa2Cu3O7-d Thin Film." Submitted to Z. Phys. High Magnetic Field Laboratory, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, PEOPLE'S REPUBLIC OF CHINA; X. W. Cao's telefax +86 551 559 1310; e-mail p03xw_cao@ipv64a.hfcas.ac.cn. 74.60.Ge; 74.72.Bk; 74.76.-w.

Kazuo Watanabe, Satoshi Awaji, and Keiichi Kimura, "Development of High Field Heat-Treatment Equipment and Relevant Applications." To be published in Jpn. J. Appl. Phys. Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-77, JAPAN. Key words: YBa2Cu3O7 bulk, GM cryocooler, superconducting magnet, heat treatment, high field.

W. Wong-Ng, L. P. Cook, W. Greenwood, and F. Jiang, "Subsolidus and Melting Phase Relationships of the PbOx-CaO-CuO System in Air." To be published in Physica C (in press). Ceramics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899; telephone (301) 975-5791; telefax (301) 990-8729; e-mail wongng@tiber.nist.gov. Key words: PbOx-CaO-CuO, superconductor-related system, phase diagrams, topological melting relationships, primary phase fields.

Joonhyun Yeo and M. A. Moore, "Simple Ginzburg-Landau Theory for Vortices in a Crystal Lattice." To be published in Phys. Rev. Lett. Department of Physics, University of Manchester, Manchester, M13 9PL, UNITED KINGDOM; e-mail yeo@a13.ph.man.ac.uk; preprint also available at cond-mat@xxx.lanl.gov (#9609142). 74.20.De; 74.60.Ge.

M. E. Zhitomirsky and M. B. Walker, "Electronic States on a Twin Boundary of a d-Wave Superconductor." Department of Physics, University of Toronto, Toronto, CANADA M5S 1A7; e-mail mzh@plato.physics.utoronto.ca; preprint also available at cond- mat@xxx.lanl.gov (#9705202). 74.25.Jb; 74.25.Fy; 74.72.Bk.

*July 7 - 9, 1997: International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials, Fitzwilliam College, University of Cambridge, United Kingdom. Topics will include (1) Growth Process: growth mechanisms and morphology, seeding effects, and faceting; (2) Processing: process optimization, rate of production, control of growth morphology, oxygenation, irradiation, hot pressing, joining, and machining; (3) Microstructural Properties: homogeneity, 211 distribution, platelet boundaries, dislocations, second-phase segregation, and radiation damage; (4) Superconducting Properties: Jc-microstructure correlation, role of defects, factors limiting Jc, and trapped field; (5) Applications: materials requirements, device design, and demonstrators development. Early registration deadline, June 30, 1997. For further information, contact Wai Lo, Workshop Secretariat, PASREG, IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom; telefax +44 1223-337074; e-mail wl103@hermes.cam.ac.uk; Web site http://www.sucon.cam.ac.uk/Workshops/PASREG.html.

July 21 - 23, 1997: U.S. Department of Energy Superconductivity Program for Electric Systems: 1997 Annual Peer Review, Washington, DC. Highlights will include public review of the applied high-temperature superconductivity (HTS) R&D carried out during FY97 by six national laboratories and their key industrial partners. Concurrent sessions will cover HTS wire and systems technology, and progress reports from the three prototype-development projects supported by the Superconductivity Partnership Initiative. For information, contact Conference Services, Energetics, telephone (410) 290-0370.

*July 27 - Aug. 1, 1997: International Cryogenic Engineering Conference and the International Cryogenic Materials Conference (Joint ICMC-CEC 1997 Conference), Oregon Convention Center, Portland, Oreg. Intended for those interested in cryogenic applications of engineering and materials. Includes special focus on superconductivity (LTS and HTS). CEC focuses on science and engineering requirements for cryogenic applications. For further information, contact Bill Warnes, Oregon State University, Mechanical Engineering Dept., Corvallis, OR 97331- 6001; telephone (541) 737-7016; e-mail warnesw@engr.orst.edu; or Nancy Wilson, Exe-Me and Company, P.O. Box 25445, Portland, OR 97298-0445; telephone (503) 292-2114; e-mail ewemeco@europa.com. Information also available at the Web site http://www.orst.edu/groups/icmc97.

*Sept. 7 - 20, 1997: Summer School on Superconductivity in Networks and Mesoscopic Structures, Certosa di Pontignano, Siena, Italy. Aimed at Ph.D. students and postdoctoral researchers. School will provide opportunity for interaction with experts from different fields and include topics such as simulation of complex dynamic systems, quantum and classical theories, Monte Carlo simulations, and others. Six days of lessons, with afternoons available for working groups and additional seminars. Proceedings to be published by World Scientific. Contact C. Giovannella, Dipartimento di Fisica, Universita di Roma "Tor Vergata", Via della Ricerca Scientifica 1, I-00133 Rome, Italy; telephone +39 6 7259 4524; telefax +39 6 202 3507; e-mail supnet@roma2.infn.it. Information also available at the Web site http://wwwas.roma2.infn.it/.

Dec. 1 - 5, 1997: MRS Fall Meeting: Symposium T -- Stability of High- Temperature Superconductors: Robust Materials for Applications. Goal of this symposium is to engage the research community in an examination of those materials aspects that will impact HTS commercialization. Abstracts are solicited in the following areas: multilayer electronics -- thermal cycling and aging effects; Josephson junctions -- interface stability and electromigration; power dependence in thin-film devices; environmental stability and passivation of HTS thin-film devices; chemical substitutions to enhance stability; phase diagrams -- thermodynamic stability of materials; grain alignment and intergrain connectivity; flux pinning, ac losses, and "trapped field" magnets; alloy, sheath, and substrate materials; and HTS systems -- reliability needs for "real world" applications. A joint session is planned with Symposium II: In-Situ Process Diagnostics and Intelligent Materials Processing. A special session will be devoted to the status of HTS commercialization efforts in the United States, Europe, and Japan. Abstract deadline, June 20, 1997 for abstracts sent via e-mail, fax or regular mail; June 23, 1997 for abstracts sent via the MRS Web site. Send abstracts to MRS Headquarters, Attention: "Abstract Enclosed," 9800 McKnight Road, Pittsburgh, PA 15237-6006; telefax (412) 366-9086; Web site http://www.mrs.org/. For information about this particular symposium, contact one of the organizers: Kirsten E. Myers, DuPont Superconductivity, Expt. Station, E304/C110, Wilmington, DE 19880-0304, telephone (302) 695-3357; telefax (302) 695-2721; e-mail myerske@esvax.dnet.dupont.com; or Ronald H. Ono, Division 814.03, NIST, 325 Broadway, Boulder, CO 80303; telephone (303) 497-3762; telefax (303) 497-3042; e-mail ono@boulder.nist.gov.

**June 14 - 19, 1998: Ninth International Conference on Modern Materials & Technologies (CIMTEC '98): Topical Symposium VI -- Science and Engineering of HTC Superconductivity, Florence International Congress Centre, Florence, Italy. Will highlight recent research advances in high-Tc oxide, organic, and other exotic superconductors. Fundamental aspects and theory, advances in materials synthesis, processing, and properties will be featured, as well as current developments in superconducting components and devices. Session topics are broadly classified into the following groups: materials, synthesis, processing, structure, and physical chemistry; physical properties; phenomenology of the superconducting state; theory of HTC superconductivity; and applications. Oral and poster presentations. Abstract deadline, September 30, 1997. Proceedings to be published. Official language is English. Contact 9th CMTEC, Forum on New Materials, Topical Symposium VI, P.O. Box 165, I-48018 Faenza, Italy; telephone +39 546-22661 or -664143; telefax +39 546-664138 or -663362.

Information

New MRS Proceedings: Microstructure Evolution During Irradiation, Vol. 354 in the MRS Symposium Proceedings Series, edited by Ian M. Robertson, Gary S. Was, Linn W. Hobbs, and Tomas Diaz de la Rubia. Discusses the evolution of a material's microstructure as a result of its interaction with energetic particles such as ions, neutrons, or electrons. Volume is interdisciplinary and emphasizes all classes of materials including metals, intermetallic compounds, ceramics, polymers, superconductors, semiconductors, and insulators. Strong focus on experimental techniques for measuring and quantifying damage and microstructure changes and computer simulation techniques for predicting and understanding this phenomena. Topics include: ion-implantation damage in semiconductors, radiation damage in metals, radiation damage in ceramics, radiation effects in polymers, and beam-induced effects. Publ. 1997; 733 pp.; price $65.00 (MRS members), $75.00 (U.S. list) and $86.00 (non-U.S. list); ISBN: 1-55899-343-6.

Solid-State Chemistry of Inorganic Materials, Volume 453 in the MRS Symposium Proceedings Series, edited by Peter K. Davies, Allan J. Jacobson, Charles C. Torardi, and Terrell A. Vanderah. This volume provides an interdisciplinary forum for discussion and exchange of ideas on both the recent advances in solid-state chemistry and their impact on the development and application of inorganic materials. Topics include: chalcogenides, synthesis and reactivity, materials synthesis, theory, optical properties, electronic and magnetic properties, dielectrics and ferroelectrics, solid-state ionics, and surfaces and interfaces. Publ. 1997; 108 papers, 746 pages; price $65.00 (MRS members), $75.00 (U.S. list) and $86.00 (non-U.S. list); ISBN: 1-55899-357-6.

Contact the Materials Research Society, Customer Services Dept., 9800 McKnight Road, Pittsburgh, PA 15237-6006; telephone (412) 367-3012; telefax (412) 367-4373.

Products and Services

Automated measurement systems: The MagLab System ^[2000] from Oxford Instruments provides a multi-measurement platform for experimental flexibility with a series of interchangeable probes for measurements in magnetic fields and low temperatures. The MagLab probes include ac, transport, heat capacity, magnetometer, and cantilever magnetometer probes. The MagLab^[AC] is cryogenically efficient ac susceptometer, the MagLab^[HC] is a full turnkey microcalorimeter which calculates heat capacity of a sample from thermal transient measurements, the MagLab^[Faraday] susceptometer functions using the Faraday technique to allow direct measurement of magnetic susceptibility, the MagLab^[VSM] is a high-speed vibrating sample magnetometer with a high sensitivity <10^[-6] noise base, and the MagLab^[JC] allows measurement of critical currents with pulsed operation for high-Tc superconductors. All instruments provide automated data collection. For information, contact Oxford Instruments, Inc., Old Station Way, Eynsham, Witney, Oxon OX8 1TL, United Kingdom; telephone +44 1865 881437; telefax +44 1865 881944; e-mail info.oiplc@oxinst.co.uk. In the U.S., contact Oxford Instruments, Inc., 30A Baker Avenue Ext., Concord, MA 01742; telephone (508) 369-9933; telefax (508) 369-6616; e-mail info@oxford.usa.com.

Postdoctoral position: Applications are invited for a possible one-year postdoc position starting early 1998. Position requires a Ph.D. degree with proven proficiency in one or more of the following areas: solid- state chemistry of superconductor oxides, borocarbides, single-crystal growth, XRD analyses, magnetic (SQUID or ac susceptibility) and resistivity measurements, and/or neutron diffraction. Candidates expecting to receive Ph.D. shortly may also apply. Basic knowledge of French will be useful. For further details contact R. Suryanarayanan, Laboratoire de Chimie des Solides, Bat. 414 Universite Paris-Sud, F- 91405 Orsay, France; telephone +33 1 69 15 47 96; telefax +33 1 69 15 47 97; e-mail suryan@isma.isma.u-psud.fr.

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. 11, #12, June 15, 1997.