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: Happy Holidays! May the new year bring you peace -- from Sreeparna, John, Charyl, Barb, Tieu, and Piyanka -- the High-Tc Update editors and staff.
RT Superconductivity?
As many of you have heard by now, a Reuters story in several newspapers recently reported possible superconductivity at 77^oF in a Li-Be-H compound studied by researchers at Lyon, France. The compound is difficult to work with because it is an explosive and burns in air. The authors have seen a diamagnetic response and hysteresis at room temperature, but there is no resistivity data because of the difficulty of making contacts to the powder sample. It appears that this was a case of premature reporting, as the evidence for superconductivity is very weak.
The news leaked out prematurely when a project graduate student defending his thesis dropped hints that the compound might be a room- temperature superconductor in a talk attended by a local reporter for the Lyon Figaro newspaper. The Reuters wire service alerted the rest of the world to the supposed breakthrough. The French scientists urge caution in interpreting these reports.
YBa2Cu3O7-d
The amplitude of displacive excitation of coherent phonons (DECP) in YBa2Cu3O7 has been observed in time-resolved spectroscopy to increase by a factor of 15 between 20 K (below Tc) and 100 K (above Tc). W.-S. Zeng and J. Kuhl (MPI-Stuttgart) have done microscopic modeling of phonon excitation and found that these amplitude changes of the A_[1g]-mode phonons are related to the existence of a Van Hove singularity (VHS) below but very close to the Fermi energy.
Measurements of the extended x-ray absorption fine structure (EXAFS) at the Y K edge of YBa2Cu3Ox for x = 6.801, 6.947, 6.968, and 6.984 at T = 20-300 K have been carried out by J. Roehler (European Synchrotron Radiation Facility and Koeln) et al. The authors report details of the local structural distortions in the CuO2 planes as a function of oxygen doping.
Other Cuprates
Coexistence of magnetism and superconductivity in R1.4Ce0.6RuSr2Cu2O10-d is reported by I. Felner et al. (Hebrew University). Magnetic ordering occurs at Neel temperatures T_N well above the superconducting transition temperature Tc: T_N ~~ 180 K and 122 K, while Tc ~~ 42 K and 32 K, for R = Gd and Eu, respectively. Magnetic susceptibility and Mossbauer spectroscopy in these materials showed that superconductivity is confined to the CuO2 planes, whereas magnetism is associated with the Ru sublattice. Scanning tunneling spectroscopy measurements revealed a superconducting gap structure for the whole sample, indicating that the materials are of single phase, simultaneously manifesting both superconductivity and magnetism.
Vortices
A preprint by V. Vinokur (Argonne) et al. provides a theoretical analysis of the phase diagram in the magnetic field and temperature (B- T) plane for vortex matter in anisotropic high-temperature superconductors. The authors consider the effects of the presence of quenched disorder and its interplay with thermal fluctuations for magnetic fields applied perpendicular to the layers. They find that there are at least three distinctly resolved phases of the vortex matter: a vortex liquid at high fields and temperatures, a low-field quasilattice vortex solid, and a high-field entangled solid. An extended Lindemann criterion is used to develop a quantitative description of the vortex-matter phase boundaries and the behavior of the transition lines with varying anisotropy and point or correlated disorder.
An experimental program has been carried out by C. Boehmer et al. (Atominstitut-Wien) for the precise determination of the lower critical field H_[c1] of a variety of high-temperature superconductors: Tl-2223, Tl-1223, Bi-2212, YBa2Cu3O7, YBa2Cu3O6.64, and YBa2Cu3O6.4 for H||c and Bi-2212 and YBa2Cu3O7 for H||ab. The authors used SQUID magnetometry and novel measuring and evaluation techniques to determine H_[c1] as a function of temperature down to about 5 K. In most cases, the values of H_[c1] obtained were smaller than those previously reported, and the temperature dependence was found to be described reasonably well by BCS theory. The authors also report values of H_[c1](0) and lambda(0) for the superconducting alkali-doped fullerenes, K3C60, Rb3C60, and RbCs2C60.
The local density of states (LDOS) in a triangular vortex lattice has been calculated by M. Ichioka et al. (Okayama) using the quasiclassical Eilenberger theory. The authors consider the case of an isotropic s- wave superconductor with material parameters corresponding to NbSe2. At high fields, where the vortex-core regions substantially overlap each other, the LDOS is a sixfold star-shaped structure with features coinciding with those obtained by scanning tunneling spectroscopy: The ray of the star points along the nearest-neighbor-vortex direction at higher energy and the next-nearest-neighbor direction at lower energy.
The magnetic-field and current-density distributions generated by a single vortex penetrating a semi-infinite superconductor has been investigated by M. W. Coffey (Colorado). The author presents closed- form London-model solutions for the fields within the superconductor, and in the half space above the superconductor, the magnetic field is expressible in terms of a Laplace-transform integral. The results are applicable to magnetic force microscopy and other probe techniques.
Theory
A preprint by I. Zutic and O. T. Valls (Minnesota) presents a method to compute the magnetic moment of a bulk, finite-size, three-dimensional anisotropic superconductor. The authors' numerically implemented perturbative procedure is based on a solution of the nonlinear Maxwell- London electrodynamic equations, and it exploits the small ratio of the finite penetration depths to the sample size.
Nonlinearities in the surface impedance Z = R + iX as a function of the surface field H are discussed in a preprint by J. Halbritter (Karlsruhe). The author stresses that a useful indicator of the source of the nonlinearities is the quantity r = delta-X/delta-R. The temperature and field dependence of this ratio, as well as its magnitude, differ for different mechanisms producing the nonlinearities.
The role of resonant tunneling for c-axis transport in the layered cuprates is considered in a preprint by A. A. Abrikosov (Argonne). Results using two models provide support for the resonant-tunneling approach.
Thin Films
Magneto-optical imaging has been used by A. E. Pashitski (Wisconsin) et al. to visualize the inhomogeneous magnetic-flux penetration into high- critical-current-density (Jc) polycrystalline TlBa2Ca2Cu3O9 (Tl-1223) films, to reconstruct the local 2D supercurrent-flow patterns J(r), and to correlate inhomogeneities of J(r) with the local crystallographic misorientation. The experiments show that the magnitude of the transport Jc is largely determined by a few high-angle grain boundaries.
Using a contactless method, G. Nakielski et al. (Hamburg) have investigated the frequency and temperature dependence of the ac conductivity sigma' + i-sigma" in the CuO2 planes of thin YBCO films deposited on (001) SrTiO3 and MgO substrates in zero magnetic field. The authors find that their results can be scaled both above and below Tc. The perfect agreement between this critical behavior and that observed in high magnetic fields suggests that the same kind of fluctuations destroy equilibrium superconductivity in the presence of vortices and that the vortex-vortex elastic interactions have no impact on the transition.
Applications
A preprint by B. Chesca (Juelich) proposes a new type of SQUID-based second-order magnetic gradiometer, operating as an RF/UHF pumped double SQUID (D-SQUID). The device consists of three quantization loops (holes) in a row, with weak links cutting across the superconducting bridges that separate the inner hole from the two outer holes. The two outer holes should be the same size, but the two weak links need not be identical. The author expects that the performance of this device will be superior to that of one-junction RF/UHF SQUID-based gradiometers.
Calculations of the levitation force on a permanent magnet above a semi- infinite superconductor have been carried out by Z. J. Yang (Argonne) using a modified critical-state model. The author finds that the levitation force depends exponentially upon the distance between the magnet and the superconductor. Analytic expressions are given for permanent magnets in the form of a point dipole, a tip of a magnetic force microscope, and a cylindrical magnet.
Other Activities
It has been found experimentally that the amplitude of the resistance noise in YBCO ceramic superconductors is very different when the same resistance value is reached either by increasing or decreasing the applied magnetic field. V. Popescu (Bucharest) et al. have carried out simulations using a 3D percolating network to explain this hysteretic behavior of the resistance noise.
Two preprints by J. M. Tranquada (Brookhaven) et al. report neutron- scattering investigations of La2NiO4+d. One of these describes the observation of low-energy spin excitations in the ordered charge-stripe phase of La2NiO4+d with d = 0.133 using inelastic neutron scattering. The spin-wave-like character of the excitations is found to be similar to the spin fluctuations observed in La2-xSrxCuO4. The authors note that evidence for incipient charge stripes in a delta = 0.105 sample has relevance for understanding spin correlations in YBa2Cu3O6.6 and possibly Nd2-xCexCuO4. The other preprint reports the observation of field-induced staggered magnetic order in La2NiO4.133 in the temperature range T > T_m = 110.5 K.
Overviews
An extensive survey of the Van Hove scenario for high-Tc superconductivity, with special emphasis on pseudogaps and striped phases, has been prepared by R. S. Markiewicz (Northeastern). The author notes that photoemission studies show that a Van Hove singularity (VHS) in the electronic density of states is close to the Fermi level in most of the high-Tc cuprates near the composition of optimum Tc, and he points out that correlation effects tend to pin the Fermi level near the VHS over an extended doping range, which can lead to nanoscale phase separation. The author also finds that experiments on underdoped cuprates provide strong confirmation that the pseudogap is driven by a splitting of the VHS degeneracy. The author even instructs us that Van Hove should be spelled with a capital V, following Belgian custom and the advice of Leon Van Hove's son, M. A. Van Hove (979 refs.).
Ph.D. Theses
The Ph.D. thesis of A. Brazdeikis (Royal Institute of Technology, Stockholm) reports on the synthesis and characterization of high- temperature superconductors using molecular-beam epitaxy (MBE). The author studied the growth of films and multilayers of Bi2Sr2Can- 1CunO2n+4+d (n = 1, 2, and 4-11), the infinite-layer compounds Ca1- xSrxCuO2, and HgBa2Can-1CunO2n+2+d (462 refs.).
Experimental studies and modeling of the physical properties of Bi2Sr2CaCu2O8+d (Bi-2212) are described in the doctoral thesis of D.-W. Hu (Eindhoven). The author carried out magnetic-relaxation, vortex- pinning, substitution, and transport experiments (184 refs.).
Contributed by Sreeparna Mitra and 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.
In a recent news release, Conductus, Inc., announced that its ClearSite(TM) receiver subsystems have been installed in a coordinated field trial at three separate and adjacent Cellcom sites in Wisconsin in order to simulate a network-wide deployment. The trial will run through the end of January to cover two full subscriber billing cycles. Cellcom administrators hope for an increased coverage for 0.6-watt portable phones between adjacent cells as well as within cells -- places where customers would otherwise experience a much higher percentage of dropped calls. In field tests conducted earlier this year with Cellcom, Conductus' ClearSite receiver subsystem enhanced base station range, coverage, and signal quality by providing increased uplink or reverse- path sensitivity, which can potentially reduce the number of base stations needed in a given area. The improved uplink is a result of combining superconductive bandpass filters with cryogenically cooled, low-noise amplifiers (LNAs). The primary focus of the trial is to develop a cost-performance model for improving coverage in rural cellular networks. The cellular industry requires a business model for widespread deployment of infrastructure equipment, and company executives believe that this trial with Cellcom represents the largest deployment of superconductive electronics in a single network. Cellcom, based in Green Bay, Wisconsin, operates approximately 100 base stations providing cellular service to several rural and urban areas in Wisconsin and Iowa. For further information, contact Duncan MacMillan, Vice President for Marketing, Conductus, Inc., 969 West Maude Ave., Sunnyvale, CA 94086; telephone (408) 523-9401; telefax (408) 523-9999.
A cooperative research and development agreement (CRADA) was signed between Oak Ridge National Laboratory (ORNL) and American Magnetics Inc. of Oak Ridge to produce a new YBCO superconducting electric current lead for powering cryogenic systems. The CRADA calls for American Magnetics and ORNL's Metals and Ceramics Division to develop a prototype lead in three months to transmit electricity more efficiently to an electromagnet in a cryogenic system manufactured by American Magnetics. The cryogenic system can be used in laboratory-scale magnets, MRI systems, and industrial magnetic fields. Researchers predict that the lead will be stronger because it will have an engineered metal, ceramic, or other structural material that is designed to contain the HTS material; it will be smaller because of a novel processing technique; and it will carry more current in a magnetic field because the superconductor is better aligned than conventional ceramic superconductors used for leads. The CRADA is funded by a DOE Small Business Innovation Research grant. For further information, contact Robert Hawsey, Superconductivity Technology Center, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6040; telephone (615) 574-6073; telefax (615) 574-6073; e-mail rav@cosmail1.ctd.ornl.gov.
For its development of high-strength HTS wires and CryoSaver(TM) current leads, American Superconductor Corporation was chosen to be one of the recipients of the R&D 100 Award, a program that annually recognizes the 100 most technologically significant new products. For information, contact American Superconductor Corporation, Two Technology Drive, Westborough, MA 01581; telephone (508) 836-4200; telefax (508) 836-4248.
Contributed by Sreeparna Mitra
A. A. Abrikosov, "Cases of Resonant Tunneling Important for High-Tc Cuprates." Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov. 73.40.Gk; 74.20.De; 74.20.Mn; 74.25.Fy; 74.72.-h.
V. C. Aguilera-Navarro, M. Casas, S. Fujita, M. G. Lopez, M. de Llano, A. Rigo, O. Rojo, M. A. Solis, and A. A. Valladares, "Can BCS and BEC be Synthesized?" Presented at the XXth Int. Workshop on Cond. Matt. Theories, Poone, India, Dec. 9-14, 1996. Contact M. A. Solis, Instituto de Fisica, UNAM, Apdo. Postal 20-364, 01000 Mexico DF, MEXICO; e-mail solis@sysul1.ifisicacu.unam.mx.
L. Ammor, A. Smina, J. C. Soret, A. Ruyter, V. Ta Phuoc, B. Martinie, J. Lecomte, B. Mercey, and Ch. Simon, "Current Density Dependence of the Activation Energy in Tl-2212 Thin Films at Weak Magnetic Fields." To be published in Physica C (in press). Laboratoire de Physique Electronique et Thermodynamique des Oxydes, Universite F. Rabelais, Parc de Grandmont, F-37200 Tours, FRANCE; +33 47 367040. 74.60.Ge.
E. Andrade, M. Jergel, J. C. Cheang-Wong, A. Conde-Gallardo, and C. Falcony, "Ion Beam Analysis of HTc Superconducting Tl-Based Films." To be published in Nuclear Instr. and Methods B. Instituto de Fisica, UNAM, Apdo. Postal 20-364, 01000 Mexico DF, MEXICO; telephone +52 5 622 50 55; telefax +52 5 622 50 09; e-mail andrade@sysul1.ifisicacu.unam.mx. Key words: HTc superconductivity, Tl-based films, IBA techniques, chemical composition, concentration depth profiles. 29.30.Ep; 74.72.Fq; 74.76.Bz.
Robert Benoist and Wilhelm Zwerger, "Critical Fields of Mesoscopic Superconductors." To be published in Z. Phys. B. European Synchroton Radiation Facility, Theory Group, B.P. 220, F-38043 Grenoble Cedex, FRANCE; telephone +33 4 76 88 27 27; telefax +33 4 76 86 24 16; e-mail benoist@esrf.fr; preprint also available at cond-mat@xxx.lanl.gov (#9611158).
Howard A. Blackstead and John D. Dow, "Rare-Earth Size-Effect on Tc in R2-zCezCuO4 Homologues." Manuscript #La96/514; to be published in Phys. Lett. Department of Physics, University of Notre Dame, Notre Dame, IN 46556; telephone (219) 631-7078; telefax (219) 631-5952; e-mail blackstd@rems1.phys.nd.edu. Key words: superconductivity, rare earths. 74.20.Fg.
G. Boehmer, G. Brandstaetter, and H. W. Weber, "The Lower Critical Field of High Temperature Superconductors." Submitted to Supercond. Sci. and Tech. Atominstitut der OEsterreichischen Universitaeten, A-1020 Wien, AUSTRIA.
M. Braden, A. H. Moudden, S. Nishizaki, Y. Maeno, and T. Fujita, "Structural Analysis of Sr2RuO4." To be published in Physica C (in press). Laboratoire Leon Brillouin (CEA-CNRS), CE-Saclay, F-91191 Gif sur Yvette Cedex, FRANCE; telefax +33 1 6908 8261; e-mail braden@bali.saclay.cea.fr.
Audrius Brazdeikis, "Epitaxial Oxide Thin Films--Synthesis and Characterization of Some High-Temperature Superconductor-Related Materials." Submitted as a Ph.D. thesis (Royal Institute of Technology, October 11, 1996). Materials Physics and Dept. of Physics, Royal Institute of Technology, 100 44 Stockholm, SWEDEN; telephone +46 8 790 6058; telefax +46 8 24 91 31; e-mail audrius@matphys.kth.se. Key words: thin oxide films, molecular beam epitaxy, high-temperature superconductor, Bi2Sr2Can-1CunO2n+4+d, HgBa2Can-1CunO2n+2+d, growth defects, surfaces, interfaces.
S. Castellazzi, M. R. Cimberle, C. Ferdeghini, E. Giannini, G. Grasso, D. Marre, M. Putti, and A. S. Siri, "Thermal Conductivity of a BSCCO(2223) c-Oriented Tape: A Discussion on the Origin of the Peak." To be published in Physica C (in press). Contact M. Putti, INFM, CNR/CFSBT, Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova, ITALY; telefax +39 10 314218.
V. V. Chabanenko, A. I. D'yachenko, H. Szymczak, and S. Piechota, "Reversible Mechanism of Magnetothermal Instabilities in Melt-Textured YBaCuO." To be published in Physica C (in press). Physical and Technical Institute, National Academy of Sciences, 340114 Donetsk, UKRAINE; e-mail chaban@host.dipt.donetsk.ua. Key words: grain alignment (textured), flux pinning, flux instability, twin boundaries, plastic deformation, YBa2Cu3O7-x.
B. Chesca, "A Three-Hole RF/UHF Double SQUID as a Natural Second-Order Magnetic Gradiometer." To be published in Physica C (in press). Forschungszentrum Juelich, Institut fuer Schicht- und Ionentechnik, D- 52425 Juelich, GERMANY.
Mark W. Coffey, "The Superconducting Half-Space With a Vortex: Closed Form Results." To be published in J. Phys. A. Department of Chemistry, University of Colorado, Denver, CO 80217. 74.20.De; 74.60.Ec; 74.20.Hi.
L. Didier, J. L. Routbort, J. F. Mitchell, and K. C. Goretta, "High- Temperature Deformation of Polycrystalline Tl2Ba2CaCu2Ox." Submitted to Appl. Supercond. 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. Endo, H. S. Chauhan, and Y. Shiohara, "Entrapment of Y2BaCuO5 Particles in Melt-Textured YBa2Cu3O7-d Crystals and its Effect on Jc Properties." Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone +81 3 3536-5703 through -5705; telefax +81 3 3536-5714 or -5717. Key words: melt processing, YBCO, macrosegregation, entrapment, flux pinning.
I. Felner, U. Asaf, Y. Levi, and O. Millo, "Coexistence of Magnetism and Superconductivity in R1.4Ce0.6RuSr2Cu2O10-d (R=Eu and Gd)." Preprint #LS6014BR; to be published in Phys. Rev. B. Racah Institute of Physics, The Hebrew University, Jerusalem 91904, ISRAEL; telephone +972 2 6585752; telefax +972 2 6586347; e-mail israela@vms.huji.ac.il. 74.10.+v; 74.62.Bf; 75.50.Ee; 76.80.+y.
J. Halbritter, "Nonlinear Surface Impedance in 'Low' and 'High' Tc Superconductors." Submitted to J. Supercond. Forschungszentrum Karlsruhe, Institut fuer Materialforschung I, Postfach 3640, D-76021 Karlsruhe, GERMANY.
Dian-wen Hu, "Investigations on Bi2Sr2CaCu2O8+z Superconductors: Magnetic Relaxation, Vortex Pinning, Substitution Effects and Transport Measurements." Submitted as a Ph.D. thesis (Eindhoven University of Technology, December 4, 1996). Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, THE NETHERLANDS; telephone +31-40 47 48 55; telefax +31-40 45 35 87; e-mail hu@tna.phys.tue.nl. Key words: superconductors, Bi2Sr2CaCu2O8+z, magnetic relaxation, vortex pinning, substitution effects, resistivity.
Masanori Ichioka, Nobuhiko Hayashi, and Kazushige Machida, "Local Density of States in the Vortex Lattice in a Type II Superconductor." Submitted to Phys. Rev. B. Department of Physics, Okayama University, Okayama 700, JAPAN; telephone +81 862 52 1111; telefax +81 862 52 7595; e-mail oka@mp.okayama-u.ac.jp; preprint also available at cond- mat@xxx.lanl.gov (#9611157). 74.60.Ec; 74.25.Jb; 61.16.Ch.
Erik W. Kvam, "Evidence for Optimal Isometric Bond Order in High Temperature Superconductors." To be published in J. Supercond. Superconductor Ventures, Inc., 169 West 80th Street, New York, NY 10024; telephone (212) 957-9000. Key words: bond order, isometric, lattice instability, fcc symmetry.
R. S. Markiewicz, "A Survey of the Van Hove Scenario for High-Tc Superconductivity with Special Emphasis on Pseudogaps and Striped Phases." To be published in J. Phys. Chem. Sol. Department of Physics and Barnett Institute, Northeastern University, 360 Huntington Avenue, Boston, MA 02115; telephone (617) 373-2916; telefax (617) 373-2943; e- mail markiewic@neu.edu; preprint also available at cond-mat@xxx.lanl.gov (#9611238). 71.27.+a; 71.38.+i; 74.20.Mn.
G. Nakielski, D. Goerlitz, Chr. Stodte, M. Welters, A. Kraemer, and J. Koetzler, "Dynamic Conductivity Near Tc of YBa2Cu3O7 Films: Vortex Glass-Like Criticality in the Absence of Externally Induced Vortices." To be published in Phys. Rev. B. Institut fuer Angewandte Physik, Universitaet Hamburg, Jungiustrasse 11, D-20355 Hamburg, GERMANY; telephone +49 40 4123 5248; telefax +49 40 4123 3589; e-mail nakielski@physnet.uni-hamburg.de. 74.60.Ge; 74.62.Bf; 74.72.Bk; 74.76.Bz.
A. E. Pashitski, A. Gurevich, A. A. Polyanskii, D. C. Larbalestier, A. Goyal, E. D. Specht, D. M. Kroeger, J. A. DeLuca, and J. E. Tkaczyk, "Reconstruction of Current Flow and Imaging of Current-Limiting Defects in Polycrystalline Superconducting Films." Submitted to Science. Applied Superconductivity Center, University of Wisconsin, Madison, WI 53706; A. Gurevich's telefax (608) 263-1087; e-mail gurevich@coefac.engr.wisc.edu.
V. Popescu, A. Stepanescu, and M. Cristea, "Simulation of Electric Resistance Noise Hysteresis in High-Tc Granular Superconductors Under a Magnetic Field." To be published in Physica C (in press). Department of Physics, University "Politehnica" of Bucharest, Splaiul Independentei 313, 77206 Bucharest, ROMANIA.
J. Roehler, P. W. Loeffen, S. Muellender, K. Conder and E. Kaldis, "Local Structure Studies of the Underdoped-Overdoped Transition in YBa2Cu3Ox: Measurement of the Yttrium X-Ray Absorption-Fine-Structure." To be published in Proc. of the NATO Adv. Study Inst. on Materials Aspects of High-Tc Supercond.: 10 Years After the Discovery, Delphi, Greece, Aug. 19-31, 1996, edited by E. Liarokapis, E. Kaldis, and K. A. Mueller (Kluwer, Dordrecht). Universitaet zu Koeln, II. Physikalisches Institut, Zuelpicherstr. 77, D-50937 Koln, GERMANY; e-mail abb12@rs1.rrz.uni-koeln.de.
S. B. Roy and P. Chaddah, "Unusual Superconducting Phenomenon in CeRu2: Effects of Nd Substitutions." To be published in Physica C (in press). Low Temperature Physics Group, Centre for Advanced Technology, Indore 452013, INDIA; telefax +91 731 481426; e-mail sbroy@cat.ernet.in.
A. V. Samoilov, "Comment on 'Pinning Strength Dependence of Mixed-State Hall Effect in YBa2Cu3O7 Crystals with Columnar Defects.'" Submitted to Phys. Rev. Lett. Department of Physics 114-36, California Institute of Technology, Pasadena, CA 91125. 74.72.Bk; 74.60.Ge; 74.60.Jg.
J. Sanchez-Canizares and F. Sols, "Self-Consistent Scattering Description of Transport in Normal-Superconductor Structures." Departamento de Fisica Teorica de la Materia Condensada, C-V and Instituto Universitario de Ciencia de Materiales "Nicolas Cabrera", Universidad Autonoma de Madrid, E-28049 Madrid, SPAIN; e-mail jsc@nuria.fmc.uam.es; preprint also available at cond-mat@xxx.lanl.gov (#9610170). 74.40.+k; 74.50.+r; 74.80.Fp; 74.90.+n.
I. Sargankova, P. Diko, J. Kovac, and M. Timko, "Microstructure and Superconducting Properties of Bi1.7Pb0.3Ca2.4Sr1.6Cu3Oy Textured by Uniaxial Pressing." To be published in Superlatt. and Microstruc. Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 043 53 Kosice, SLOVAK REPUBLIC; e-mail sarganek@linux1.saske.sk.
J. M. Tranquada, P. Wochner, and D. J. Buttrey, "Spin Dynamics in an Ordered Stripe Phase." Department of Physics, Brookhaven National Laboratory, Upton, NY 11973; telephone (516) 344-7547; telefax (516) 344-2918; e-mail jtran@bnl.gov; preprint also available at cond- mat@xxx.lanl.gov (#9612007). 75.30.Ds; 75.30.Fv; 71.45.Lr; 74.72.-h.
J. M. Tranquada, P. Wochner, A. R. Moodenbaugh, and D. J. Buttrey, "Field-Induced Staggered Magnetic Order in La2NiO4.133." Department of Physics, Brookhaven National Laboratory, Upton, NY 11973; telephone (516) 344-7547; telefax (516) 344-2918; e-mail jtran@bnl.gov; preprint also available at cond-mat@xxx.lanl.gov (#9611091). 71.27.+a; 75.50.Ee; 75.30.Fv; 71.45.Lr.
P. Vigoureux, M. Braden, A. Gukasov, W. Paulus, P. Bourges, A. Cousson, D. Petitgrand, J. P. Lauriat, M. Meven, S. N. Barilo, D. I. Zhigunov, P. Adelmann, and G. Heger, "Study of the Structural Phase Transition in Gd2-xCexCuO4." To be published in Physica C (in press). Contact M. Braden, Laboratoire Leon Brillouin (CEA-CNRS), CE-Saclay, F-91191 Gif sur Yvette Cedex, FRANCE; telefax +33 1 6908 8261; e-mail braden@bali.saclay.cea.fr.
V. Vinokur, B. Khaykovich, and E. Zeldov, "Lindemann Criterion and Vortex-Matter Phase Transitions in High-Temperature Superconductors." Submitted to Nature. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e- mail janice_coble@qmgate.anl.gov.
W. Wong-Ng and L. P. Cook, "Cation Non-Stoichiometry of the BaCuO2+x Phase." To be published in Physica C (in press). Ceramics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899; telefax (301) 975-2125; e-mail wongng@tiber.nist.gov.
X. S. Wu, W. M. Chen, X. Jin, and S. S. Jiang, "Mechanochemical Effects of Grinding on the YBa2Cu3Ox Superconductor." National Laboratory of Solid State Microstructures and Center for Advanced Studies in Science and Technology of Microstructures, Nanjing University, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA.
Z. J. Yang, "Levitation Force on a Permanent Magnet over a Superconducting Plane: Modified Critical-State Model." To be published in J. Supercond. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e- mail janice_coble@qmgate.anl.gov. Key words: magnetic levitation, high-Tc superconductor, critcal-state model, magnetic-force microscope. 85.25.Ly; 41.20.Gz; 74.60.Jg; 74.72.-h; 61.16.Ch.
Shuichi Yoshikawa, Masaaki Nemoto, Kazuhiro Shimaoka, Kazuya Niki, Isao Yoshida, and Yorinobu Yoshisato, "Ka-Band Performance of Step-Edge Josephson Junctions Using Tl2Ba2CaCu2Ox Films on MgO Substrates." To be published in Physica C (in press). Tsukuba Research Center, SANYO Electric Co., Ltd., Tsukuba 305, JAPAN. Key words: Tl2Ba2CaCu2Ox, Josephson junction, responsivity, mixing.
W.-S. Zeng and J. Kuhl, "Displacive Excitation of Coherent Phonons in YBa2Cu3O7: An Optical Evidence for the Van-Hove Singularity." University of Rochester, 240 East River Road, Rochester, NY 14623; telephone (716) 275-1929; telefax (716) 273-1014; e-mail zeng@ee.rochester.edu. 78.47.+p; 74.25.Gz; 74.25.Jb; 71.15.Fv.
Ji-Ping Zhou, Rung-Kuang Lo, Steven M. Savoy, Mark Arendt, Jeff Armstrong, Du-Yu Yang, John Talvacchio, and John T. McDevitt, "Environmental Degradation Properties of YBa2Cu3O7-d and Y0.6Ca0.4Ba1.6La0.4Cu3O7-d Thin Film Structures." Contact John T. McDevitt, Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712-1167. Key words: high-Tc thin film, superconductor lifetime measurement, corrosion, surface characterization, environmental degradation.
Igor Zutic and Oriol T. Valls, "Numerically Implemented Perturbation Method for the Nonlinear Magnetic Moment of an Anisotropic Superconductor." Research Report UMSI 96/223. School of Physics and Astronomy and Minnesota Supercomputer Institute, University of Minnesota, Minneapolis, MN 55455-0149.
*Feb. 6 - 7, 1997: The DOE 1997 Wire Development Workshop, Marriott/Bay Point in Panama City, Florida. Objectives are to hear reports on research progress, trends, and problems in HTS coated conductor and powder-in-tube wire; review critical program needs and develop strategies for addressing issues in BSCCO wire and its applications, YBCO coated conductors, and low ac loss conductors; and interact with colleagues to further strengthen collaborative efforts in the program. Plenary sessions followed by working groups that address issues in that topical area. For more information, contact Jim Daley, Department of Energy, telephone (202) 586-1165; Chris Platt, Department of Energy, telephone (202) 586-8943; or Craig Matzdorf, Energetics, telephone (410) 290-0370.
*Feb. 28 - March 4, 1997: Fifth International Conference on Materials and Mechanisms of Superconductivity and High-Temperature Superconductors (M2S-HTSC-V), Beijing, China. Two plenary sessions, 30-33 microsymposia and oral sessions (three or four parallel sessions, at least two sessions to be reserved for latest new results and outstanding post deadline contributions), three tutorial sessions, and poster sessions. Topics include high-Tc materials; physical properties of high-Tc materials; magnetism and superconductivity; vortices, pinning, and flux melting; thin films and multilayers; Josephson junctions; applications; heavy fermions; organic superconductors; fullerenes; and theory. Exhibition of high-Tc superconducting materials, low-temperature experimental appliances, and cryogenic engineering and refrigeration instruments. Conference language is English. Abstract and manuscript deadline, January 31, 1997.** For information, contact D. Jin, M2S-HTSC- V Secretariat, Cryogenic Laboratory, Chinese Academy of Sciences, P.O. Box 2711, Beijing 100 080, People's Republic of China; telephone +86 10 6 255 1143; telefax +86 10 6 256 4049; e-mail djin@cl.cryo.ac.cn; Web site http://sun1.bham.ac.uk/hey/conferences/. **Note revised abstract deadline and telephone numbers.
*April 7 - 9, 1997: Fourth HTS Workshop on High Frequency Applications of Thin Films, Fabrication, Passive and Active Devices, Oxford, United Kingdom. Follows previous three successful HTS Workshops held at the University of Twente in 1994, 1995, and 1996. Five sessions comprising the Workshop will cover: 1) the deposition of thin films of HTS; 2) the microwave properties of HTS; 3) the design, fabrication, and performance of HTS passive microwave devices; 4) the fabrication of Josephson junctions in HTS; and 5) the applications of HTS Josephson devices. Oral and poster contributions are solicited; proceedings to be published. Further details available from D. Dew-Hughes, A. P. Jenkins, or C.R.M. Grovenor, Department of Engineering Science; telefax +44 1865 273010 or -273764; e-mail grovenor@materials.oxford.ac.uk; Web site http://www.materials.ox.ac.uk/Materials/Conferences/hts4thinfilms.html. Registration can also be carried out via the Web page.
*May 4 - 9, 1997: Fullerenes: Chemistry, Physics and New Directions IX, Montreal, Canada. Sponsored by the Fullerenes Group of the Electrochemical Society. Symposium provides forum for the presentation of latest developments on these new allotropes of carbon, including nanotubes and nanopolyhedra. Part of the 191st meeting of the Electrochemical Society. Papers are solicited. Topics include technology & polymers, theory, superconductivity, organic functionalization, photoexcited states, gas phase/mass spectrometry, extraction/purification/solubility, diffraction studies, metallofullerenes, surface/film studies, thermodynamics, electrochemistry/ESR, solid-state physics, and others. Abstract deadline, January 1, 1997. Papers to be published. For further information, contact Karl M. Kadish, Department of Chemistry, University of Houston, Houston, TX 77204-5641; telephone (713) 743-2740; telefax (713) 743-2745; e-mail: kkadish@uh.edu or Rodney S. Ruoff, Department of Physics, Washington University, CB 1105, One Brookings Drive, St. Louis, MO 63130-4899; telephone (314) 935 8746; telefax (314) 935-6219; e-mail ruoff@howdy.wustl.edu. Information also available at the Web site http://www.electrochem.org.
*June 15 - 18, 1997: Third Joint ISTEC/MRS International Workshop on Superconductivity: Suitable Materials and Processing for HTS Applications Towards the Next Decade, The Royal Waikoloan, Big Island, Hawaii. Will mainly be a single-session meeting with significant time allotted to encouraging the exchange of information among participants. Regular sessions titles are: processing of HTS bulk; processing of HTS wire, tapes, and thick films; crystal growth related to HTS processing of bulk and films; thin-film processing for rf applications; and fabrication and control of HTS junctions for digital circuits. Rump sessions: ac losses, vortex dynamics, and pinning; and SQUID and sensor applications. Invited and contributed oral presentations and posters. Abstract deadline, January 10, 1997. Contact Koji Kajimura, Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305, Japan; phone +81 298 54-5003; fax +81 298 54-5070; e-mail kajimura@ etl.go.jp or Eric Hellstrom, Department of Materials Science & Engineering, University of Wisconsin at Madison, Madison, WI 53706; phone (608) 263- 9462; fax (608) 263-1087.
*June 26 - 28, 1997: 6th International Superconductive Electronics Conference (ISEC'97), Intercontinental Hotel, Berlin, Germany. Conference will encompass all aspects of superconductive electronics including the enabling technologies, devices, circuits, instrumentation, theory, and applications. Topics will range from very-low-frequency SQUIDs to ultra-high-speed digital circuits. Of special interest will be the progress towards commercial products. No parallel sessions. Oral and poster sessions. Topics will include: physics of superconductive devices, superconducting device fabrication, process technology, superconductive digital and analog circuits and devices, new devices such as superconductive transistors and power devices, applications and instrumentation, and others. Abstract deadline, February 15, 1997. For further information, contact ISEC'97 Conference Secretariat, Dipl. Phys. Silvia Knappe, Physikalisch-Technische Bundesanstalt, Abbestr. 10-12, D-10587 Berlin, Germany; telefax +49 30 3481-490; e-mail isec97@ptb.de; Web site http://www.lab1033.berlin.ptb.de/10/102/isec97/start.htm.
*July 27 - Aug. 1, 1997: International Conference on Magnetism (ICM '97), Cairns Convention Center, Cairns, Australia. Includes Symposium on Strongly Correlated Electron Systems. Designed to survey the developments in the field of magnetism in the previous three years. Format consists of plenary lectures, workshops, lecture sessions, and posters. Abstract deadline, January 17, 1997. Proceedings to be published in J. Magnetism and Mag. Mater. For information, contact the International Conference on Magnetism, 108 Church Street, Hawthorn Victoria, Australia 3122; telephone +61 3 9819 3700; telefax +61 3 9819 5978; e-mail icm@meetingplanners.com.au.
Sept. 1 - 12, 1997: NATO Advanced Study Institute on the Gap Symmetry and Fluctuations in High-Tc Superconductors, Institut d'Etudes Scientifiques de Cargese, Corse, France. Objective is to give advanced lectures on the most recent progress in understanding of the physics of high-temperature superconductors with a special emphasis on the symmetry of the superconducting gap and critical fluctuations. Pedagogical explanation of various theoretical models and a direct comparison with recent (often controversial) experiments is the central point of this Advanced Study Institute. A dedicated www site with more details will be announced in January 1997. For preliminary information contact Davor Pavuna, telephone +41 21-6933301; telefax +41 21-6934666; e-mail pavuna@eldp.epfl.ch.
*Sept. 14 - 18, 1997: Conference on Spectroscopies in Novel Superconductors (SNS '97), Sea Crest Oceanfront Resort and Conference Center, Falmouth, Cape Cod, MA. Conference sponsored by the College of Arts and Sciences as part of centennial celebration of the founding of Northeastern University. For further information, contact Arun Bansil, Conference Chair, Department of Physics, Northeastern University, Boston, MA 02115; telephone (617) 373-2923; telefax (617) 373-294 or Julie Pumphrey, Conference Secretary, The Barnett Institute, Northeastern University, Boston, MA 02115; telephone (617) 373-2868; telefax (617) 373-2855.
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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.
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Project Director/Editor: Sreeparna Mitra Science Editor: John R. Clem High-Tc Update, Vol. 11, #1, January 1, 1997.