Published for the Division of Materials Sciences, Office of Basic Energy Sciences, USDOE, under Contract W-7405-eng-82 with the Ames Laboratory, Iowa State University. Funded by DMS/BES/USDOE, ARPA, NSF, and other agencies, organizations, and individuals.

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:

Columnar Defects

The pinning efficiency of tilted columnar defects produced upon irradiation of single crystals of Bi2Sr2CaCu2O8+d (Bi-2212) with 6 GeV Pb ions has been investigated experimentally by S. Hebert et al. (Caen). The authors found a regime at high temperatures and low fields where the critical current density was higher when the tracks were at an angle theta_i = 75 degrees relative to the c axis than when the tracks were parallel to the c axis. The authors attribute the enhancement to the increase of the pancake-vortex pinning energy resulting from the larger size of the track projection on the ab planes.

The structural and transport properties of interacting vortex lines in the Bose-glass phase of heavy-ion-irradiated superconductors have been studied by C. Wengel (Goettingen) and U. C. Taeuber (TU-Muenchen) using Monte Carlo simulations near the matching field B_[phi], where the densities of vortices and columnar defects are equal. For a completely random columnar pin distribution in the xy plane transverse to the magnetic field, the authors find that the repulsive vortex interactions destroy the Mott-insulator phase that has been predicted to occur at B = B_[phi]. On the other hand, for ratios of the penetration depth to average defect distance lambda/d <= 1, the authors show that characteristic remnants of the Mott-insulator singularities remain visible in the magnetization, bulk modulus, and relaxation as B is varied near B_[phi].

The depinning of a weakly driven (F << F_c) pancake vortex from a columnar defect in a Josephson-coupled superconductor, where F denotes the force acting on the vortex and F_c is the critical force, has been addressed theoretically by D. A. Gorokhov and G. Blatter (ETH-Zurich). The authors find that the transition from thermally assisted quantum to classical behavior is second-order-like with the temperature Tc of the transition scaling as F^[4/3].

A complementary paper by D. A. Gorokhov and G. Blatter (ETH-Zurich) describes an analysis of the thermally activated depinning of an elastic string (line tension epsilon) governed by Hall dynamics from a columnar defect modeled as a cylindrical well of depth V_0 for the case of a small external force F. At high temperatures, the authors find the decay rate to be proportional to F^[5/2]T^[-1/2]exp[F_0/F - U(F)/T], where F_0 is a constant of the order of the critical force F_c and U(F) ~ (epsilonV_0)^[1/2]V_0/F is the activation energy.

Vortex Lattices

A sharp resistance drop associated with vortex-lattice melting has been observed by X. G. Qiu (Leuven) et al. in high-quality YBa2Cu4O8 single crystals. The melting line was found to be described well by the anisotropic Ginzburg-Landau theory. The authors find two thermally activated flux-flow regions, separated by a crossover line B_[cr](T) = (1406.5)(1 - T/Tc)/T (with Tc = 79 K, B in T, and T in K). The authors thus argue that as the field or temperature increases, the vortex lattice in YBa2Cu4O8 single crystals first melts into a disentangled line liquid, which then undergoes a 3D-2D decoupling transition into a pancake-vortex liquid with a loss of correlation along the field direction.

Experiments by E. Rodriguez (Buenos Aires and Barcelona) et al. show evidence for vortex-lattice melting in oxygen-deficient YBa2Cu3O6+x. The melting line is pushed to lower fields and temperatures because of increased anisotropy due to oxygen depletion. An upper limit of about 150 is placed on the anisotropy parameter gamma.

Piezolever torque magnetometry has been used by C. Bergemann (Cambridge) et al. to measure the magnetization of superconducting Tl2Ba2CuO6+d (Tl- 2201). In three crystals with different levels of oxygen overdoping, the magnetization in fields above the irreversibility line was found to depart from the behavior M ~ ln(etaHc2/H) for a simple London-like vortex liquid. In the strongly overdoped crystal (Tc = 15 K), the remnant superconducting order above the irreversibility line was found to be characterized by a linear diamagnetic response (M ~ H) persisting well above Tc and up to the highest field employed (10 T).

The effects of random dilution of junctions in a two-dimensional Josephson-junction array in a magnetic field have been considered theoretically by M. Benakli (ICTP-Trieste) et al. The authors numerically studied the behavior of the array as a function of the probability x that the Josephson coupling between adjacent superconducting grains is zero, and they found a range of x values for which the array behaves as a zero-temperature vortex glass.

Motivated by the problem of weak collective pinning of vortex lattices in high-temperature superconductors, H. Bucheli (ETH-Zurich) et al. have studied the model system of a four-dimensional elastic manifold with N transverse degrees of freedom (4+N model) in a quenched disorder environment. The authors used a real-space renormalization-group approach to calculate the size R_c of collectively pinned elastic domains and the critical force F_c needed to drive these domains into motion.

Plastic Flow of the Vortex Lattice

An experimental study of current-voltage characteristics of a superconducting 2H-NbSe2 single crystal subjected to a dc magnetic field of 0.5 T perpendicular to the layers has been carried out by W. Henderson and E. Y. Andrei (Rutgers). The authors found that if the applied current is switched periodically between -30 mA and +30 mA, an amplitude below the dc critical current of 50 mA, the measured voltage is about 30% of what it would be in the free flux-flow limit. On the other hand, if the current is switched between zero and +30 mA or between zero and -30 mA, the voltage response is essentially zero. The authors also find that the vortex lattice retains a memory of the frequency with which it was driven long after the current is turned off. The authors point out that some of these phenomena are similar to plasticity effects observed in soft metals, and that they give new insight into the processes of plastic flow and depinning.

ac Losses

Alternating magnetic field losses for (Bi,Pb)2Sr2Ca2Cu3O10+d [(Bi,Pb)- 2223] multifilamentary tapes with a mixed Ag-BaZrO3 matrix for coupling- loss reduction have been measured and analyzed by K. Kwasnitza (PSI) et al. at 77 K and at frequencies up to 100 Hz. Because of the oxide barriers around the filaments, the effective transverse electrical resistivity in the matrix increased by a factor of eight, which gave a corresponding modification of the frequency dependence of the coupling losses. The authors note that this is a promising step in the development of low-loss high-Tc superconductors for 50 Hz applications.

The influence of both bulk and edge pinning on the response of a thin- film superconductor to an oscillating magnetic field has been considered theoretically by I. L. Maksimov and A. A. Elistratov (Nizhny Novgorod). The authors construct hysteretic magnetization curves for one cycle of the magnetic field, and they calculate the dependence of the hysteretic losses on the field amplitude. The losses are zero for ac field amplitudes less than the first-vortex-entry field H_1.

Zn and Ni Impurities

Using muon spin rotation (muSR), C. Bernhard (MPI-Stuttgart) et al. have searched for Zn- and Ni-impurity-related magnetic moments in underdoped cuprates. The authors found that the moments previously attributed to Zn impurities [P. Mendels et al., Phys. Rev. B 49, R10035 (1994)] exist already in the pure compound and most likely arise from the antiferromagnetically correlated Cu(2) (CuO2-plane) spins. No direct evidence was found for additional Zn- or Ni-related magnetic moments. The authors did observe, however, a Ni-induced magnetic freezing transition, which indicates a stronger magnetic coupling for the Ni moments than for the hypothetical Zn-induced moments.

The effects of magnetic and nonmagnetic impurities upon Tc in s-wave and d-wave superconductors, taking into account a correction due to local variations of the gap function near impurity sites, have been calculated by M. E. Zhitomirsky and M. B. Walker (Toronto). The correction, which is of the order of Tc/E_F, becomes important for short-coherence-length superconductors and generally reduces the pair-breaking effect. The authors note that in s-wave superconductors small amounts of nonmagnetic impurities can increase the transition temperature.

A preprint by H. A. Blackstead (Notre Dame) and J. D. Dow (Arizona State) reports that in all high-temperature superconductors that have been measured, except BCS-like Nd2-zCezCuO4, Ni and Zn impurities suppress Tc by virtually the same amount, which the authors claim is inconsistent with cuprate-plane superconductivity resulting from either (a) BCS-like (phonon-like) polarization pairing or (b) spin-fluctuation pairing. The authors stress that the observed Tc suppression in all such superconductors, including Nd2-zCezCuO4, is consistent with BCS- like charge-reservoir superconductivity.

RBa2Cu3O7-d

NMR and NQR measurements have been performed by B. Grevin (Grenoble) et al. on Cu(1) chain sites in nonsuperconducting PrBa2Cu3O7 between 4.2 K and 300 K. The static and dynamic NMR and NQR parameters were found to undergo a crossover at 180 K, and an energy gap in the electronic excitations was found to open below 120 K, as revealed by the temperature dependence of 1/T_1. The results are consistent with a charge-density wave (CDW) occurring in the quasi-one-dimensional CuO3 chains.

Measurements of geometrical effects upon the normal-state magnetoresistance of YBa2Cu3O7 thin films patterned into a Corbino disk, a square, and a strip are reported by W. Goeb (Wien) et al. A systematic magnetoresistance difference, called the geometrical magnetoresistance (GEMR), between the Corbino and strip samples was observed. The authors note that the GEMR arises from bending of the current trajectories in the transverse magnetic field and is proportional to the square of the Hall angle.

The effects of neutron irradiation and annealing upon Tc and Jc in YBa2Cu3O7-d single crystals are discussed in a preprint by F. Sauerzopf (Atominstitut-Wien). The author explains some of the results in terms of the mobility of smaller defects and their interaction with the radiation-induced defect cascades.

A preprint by G. J. Schmitz et al. (ACCESS) proposes a concept for producing textured coatings of RBa2Cu3O7-d superconductors. The process involves the use of geometrically arranged reactive precursors on the substrate.

Bi Cuprates

A high-resolution magneto-optical technique has been used by Z. W. Lin (New South Wales) et al. to visualize the magnetic-flux distribution in (Bi,Pb)-2223/Ag multifilamentary tapes. Magnetic-flux profiles are presented for a seven-filament sample with both exposed and silver- sheathed filaments. The study was carried out over the temperature range 40-80 K for applied magnetic fields in the range 0-560 G and dc currents up to 60 A.

Other Cuprates

A preprint by N. E. Hussey (Tokyo) et al. reports several remarkable new features in the normal-state c-axis magnetoresistance in the underdoped cuprate YBa2Cu4O8. The low-T c-axis resistivity rho_c(T) is metallic, but when a magnetic field is applied perpendicular to the chains (B||a), rho_c changes dramatically, and at sufficiently high fields, rho_c begins to show localized behavior. This observation reveals the critical role of the CuO chains in metallizing the c-axis at low fields. In the high-field range where rho_c(T) has insulating behavior, Delta[rho_c]/rho_c varies linearly with field, rather than quadratically, suggesting a new magnetoconductivity regime in a state of lower dimensionality.

The angular dependence of the resistivity rho(theta), where theta is the angle of B relative to the c axis, has been measured by F. Warmont et al. (Caen) in the superconducting transition region of (Tl2/3Bi1/3)Sr2CaCu2Ox [(Tl,Bi)-1212, Tc = 84 K] crystals. The authors were able to scale the resistivity using an anisotropic effective-mass model with an anisotropy parameter gamma = (m_c/m_[ab])^[1/2] of 9-12, which is larger than in YBa2Cu3O7-d (gamma ~~ 5), but much smaller than in Bi-2212 (gamma > 200) or Tl-2212 compounds (gamma > 60).

Measurements of the linear thermal expansion coefficients alpha_i at the superconducting transition temperature Tc and measurements of the hydrostatic pressure dependence dTc/dP of high-quality single crystals of Sm2-xCexCuO4-y have been carried out by M. Kund (Garching) et al. The uniaxial stress dependencies dTc/d[sigma_i] were deduced thermodynamically from the observed discontinuous changes in alpha_i at Tc. The uniaxial stress effects along the a and c directions are dTc/d[sigma_a] = -5.78+-1.6 K/GPa and dTc/d[sigma_c] = +11.66+-3.5 K/GPa, respectively. Their sum agrees well with the measured dTc/dP near zero. Thus, a decrease in the interlayer spacing has a strong positive effect on Tc, and a decrease in the intralayer atomic spacing has a strong negative influence on Tc.

A nearly single-phase Pb-1234 compound has been synthesized by T. Tamura et al. (SRL-ISTEC) in an oxidizing atmosphere using a high-pressure technique. From an SEM-EDX analysis, the authors postulate a tentative composition of (Pb0.5Sr0.3Cu0.2)Sr2.0(Ca2.8Sr0.2)Cu4.0O9+d for the Pb- 1234 phase. The maximum Tc for the as-prepared sample was 107 K, which is almost independent of the nominal oxygen content, and it decreases slightly upon annealing in Ar, suggesting that the as-prepared Pb-1234 phase is slightly underdoped.

Thin Films

In-situ studies of the superconducting and normal-state transport properties in partially oxygen-depleted, metallic YBa2Cu3O7-d (midpoint Tc ~~ 52 K) thin films exposed to long-term white-light illumination (photodoping) are reported by C. Stockinger (Wien) et al. The authors found that the photoinduced enhancement of the superconducting transition temperature Tc exhibited essentially the same temperature dependence as the enhancement of the Hall number, being largest (Delta[Tc] ~~ 2.6 K) for the illumination performed at high temperatures. The authors thus conclude that the Tc enhancement results from the change of the carrier density rather than from a change in mobility of the charge carriers.

As reported by Q. X. Jia (Los Alamos) et al., superconducting YBa2Cu3O7- d (YBCO) films with a surface resistance of 0.86 milliohm at 10 GHz and 76 K have been grown on polycrystalline ferrite yttrium iron garnet (YIG) substrates. The chemical and structural mismatches between YBCO and YIG were solved by using a double buffer layer of biaxially oriented yttria-stabilized zirconia (YSZ) and CeO2, where the YSZ was deposited using an ion-beam-assisted-deposition (IBAD) technique. The YBCO films were c-axis-oriented and had a superconducting transition temperature above 88 K with a transition width less than 0.3 K, giving a critical current density above 10^6 A/cm^2 in self field at 75 K. In an applied magnetic field of 1 T perpendicular to the film surface, the films maintained a critical current density Jc of over 2 x 10^5 A/cm^2 at 75 K. The authors note that the ability to produce such high-quality YBCO films on polycrystalline YIG substrates should make it possible to fabricate integrated magnetically tunable microwave components on a cost-effective single ferrite platform.

Applications

A preprint by J. C. Gallop (NPL-Teddington) et al. proposes a novel form of cryogenic primary thermometer, called a quantum roulette noise thermometer (QRNT), based on flux quantization in a high-temperature superconducting ring interrupted by Josephson junctions. The principle of the QRNT is that the flux state of a double-junction SQUID ring (in thermal contact with a heat bath whose temperature is to be measured) is allowed to evolve freely. At regular intervals the quantized internal state of the ring is interrogated via a second SQUID detector, allowing a probability distribution of flux states to be built up, from which the absolute temperature may be directly derived. Unlike other superconductivity-based noise thermometers, this device is essentially dissipationless, requires no input or output connections, and may be remotely interrogated. The QRNT has the potential to provide high accuracy with short measuring times. The authors describe the principles behind the device and present preliminary experimental data.

Experimental results on YBCO thin-film bicrystal junctions in which additional metallic shunt resistors are added by in-situ evaporation of gold or silver are reported by L. Hao (NPL-Teddington and Strathclyde) et al. These junctions are intended for use in the development of a Josephson noise thermometer for primary temperature scale use. The authors compare their results with the predictions of a simple model, and they discuss implications for the potential accuracy of the proposed thermometer.

Magnetometers based on direct-coupled YBa2Cu3O7-d superconducting quantum interference devices (SQUIDs) with SQUID inductances of 50 pH and 100 pH on 10 mm x 10 mm 24 degrees SrTiO3 bicrystal substrates have been fabricated by F. Ludwig et al. (PTB-Berlin). The best magnetometer had a white noise of 41 fTHz^[-1/2] and a 1/f corner at 2 Hz, including electronics and environmental noise. High-quality magnetocardiograms recorded in the Berlin magnetically shielded room (BMSR) illustrate that the sensors are suitable for biomagnetic multichannel systems.

Theory

A preprint by C. P. Burgess (McGill) et al. considers some of the consequences of S.-C. Zhang's [Science 275, 1089 (1997)] proposal that the effective Hamiltonian describing high-Tc superconductivity in cuprate materials has an approximate SO(5) symmetry relating the superconducting and antiferromagnetic phases. The authors show that robust consequences of this proposal are potentially strong optical conductivities and Raman scattering rates in the antiferromagnetic phase, due to the electromagnetic response of the doubly charged pseudo Goldstone bosons which must exist there. This provides strong constraints on the properties of the bosons, including their mass gap and velocity.

Two papers by R. S. Markiewicz and M. T. Vaughn (Northeastern) point out that the instabilities (either nesting or pairing) associated with the high-Tc cuprates can be described by an SO(6) transformation group. There are two independent six-dimensional representations (superspins). One superspin combines Zhang's five-component superspin with a flux- phase instability; the other involves a charge-density wave, s-wave superconductivity, and an exotic spin current. The authors note that SO(6) is the smallest group that can describe both striped phases and superconductivity. The authors also point out that the various nesting and pairing instabilities of the generalized Van Hove scenario can be classified via an SO(8) spectrum-generating algebra.

Recent angle-resolved photoemission spectroscopy (ARPES) measurements above Tc in the high-Tc cuprates have revealed a loss of spectral weight in the incoherent signal at the Fermi surface crossing whose magnitude seems to have the d-wave symmetry of the superconducting gap. A preprint by G. J. Kaye (Cambridge) presents a calculation of the signal expected from a mixed state of polarons and bipolarons. The results indicate that the "d-wave" pseudogap feature can be interpreted as a signature of the internal symmetry of the bipolarons rather than that of a true gap.

A preprint by R. A. Klemm (Argonne) et al. reports calculations of the Josephson critical current for a highly anisotropic layered superconductor consisting of two identical parts that are twisted with respect to each other by an angle phi_0 about the c axis. The authors derived and studied the effective Lawrence-Doniach model appropriate for the cases of pure s-wave and d_[x^2-y^2]-wave order parameters, a dominant d_[x^2-y^2] and subdominant d_[xy] mixed order parameter, and a dominant d_[x^2-y^2] and subdominant s-wave mixed order parameter. The authors suggest that Josephson tunneling across c-axis twist junctions can be a useful tool for probing the superconducting order-parameter symmetry.

The consequences of a half-filled generalized Hubbard chain with electron-hole-symmetric correlated hopping and on-site and nearest- neighbor repulsions U and V have been considered by A. A. Aligia and E. R. Gagliano (Bariloche). In addition to the insulating charge- and spin-density-wave phases for large V and U, respectively, the authors identify a phase with dominant superconducting correlations at large distances for small U and V.

Density-functional calculations based on the local density approximation (LDA) have been carried out by V. Meregalli and S. Y. Savrasov (MPI- Stuttgart) to investigate the phonon spectrum of Ba0.6K0.4BiO3. The authors also include the effects of anharmonic contributions to the electron-phonon coupling constant lambda and find that the total (harmonic plus anharmonic) lambda = 0.34, which is too small to explain the high-temperature superconductivity (Tc ~ 30 K) in this material.

Other Activities

As reported by M. M. Leivo et al. (Jyvaeskylae), a normal- metal/insulator/superconductor (NIS) tunnel junction can be used to cool electrons in the normal metal by biasing the junction with a voltage V slightly below Delta/e. In this case, only hot electrons can tunnel from the normal electrode into the superconductor. After an electron tunnels, a quasiparticle of energy Delta is produced in the superconductor, work eV is done by the power supply, and the thermal energy in the normal metal is reduced by Delta-eV. Because of the symmetry with bias voltage, two NIS junctions in series can form an efficient microrefrigerator. So far, the authors' SINIS microrefrigerator has been capable of reaching electronic temperatures of about 100 mK starting from 300 mK. To achieve appreciable refrigeration of the underlying lattice, the microrefrigerator must be thermally decoupled from the bulk substrate. The authors have experimentally demonstrated the reduction of lattice temperatures of a few mK at 200 mK by extending the normal electrode onto a thin dielectric membrane.

The effects of a crossed ac magnetic field (h_[ac]||ab) upon the magnetization hysteresis curves of melt-textured and single-crystal YBCO for H_[dc]||c have been investigated by S. K. Hasanain et al. (Islamabad). The authors found that the magnitude of the dc magnetization not only decreases with increasing h_[ac]amplitude but also decreases as the logarithm of the ac field frequency. In these experiments, currents induced in the sample by the crossed ac magnetic field flow parallel to the vortices and initiate flux-line-cutting processes, thereby altering the magnitude of B inside the sample.

Overviews

Tunneling in high-Tc cuprates has been reviewed by J. Lesueur (Orsay) et al. After an introduction to tunneling spectroscopy and the Josephson effect in low-temperature superconductors, the authors discuss the corresponding phenomena in the high-temperature superconductors, emphasizing the behavior in planar tunnel junctions (128 refs.).

A chapter on the synthesis, structure, and physical properties of the Hg-based superconductors Hg-12(n-1)n and (Hg,Tl)-22(n-1)n has been prepared by S. Adachi (SRL-ISTEC) et al. At ambient pressure, the Tc's of HgBa2CuO4+d (Hg-1201), HgBa2CaCu2O6+d (Hg-1212), HgBa2Ca2Cu3O8+d (Hg- 1223), and HgBa2Ca3Cu4O10+d (Hg-1234) are 97 K, 127 K, 135 K, and 123 K, respectively (73 refs.).

Contributed by John R. Clem

Contents: Technology News is on page 6; Preprints begin on page 7; Coming Events begin on page 11; and FYI is on page 13.

High-Tc Update is available without charge to interested persons. Recipients are expected to participate in this information exchange by sending us preprints, reprints, meeting news, research news, etc. Contributions to defray the cost of newsletter printing and mailing are welcome.

TECHNOLOGY NEWS (Also see Applications section of Nota Bene.)

This section describes progress in manufacturing, product development, and technology transfer in the high-Tc superconductivity field. Please send your contributions (product development information, news regarding technology transfer efforts, or any information you would like to share about your corporation or laboratory) to the editor.

Researchers at Berkeley Lab have developed a new design for high-Tc SQUID systems that eliminates excess low-frequency noise in the SQUIDs and SQUID-based magnetometers operating in an ambient magnetic field. This intrinsic magnetic noise was previously a major impediment to the application of high-Tc SQUIDs in the earth's magnetic field. When traditional high-Tc SQUIDs, made from YBa2Cu3O7-x (YBCO) are cooled through their transition temperature to their operating temperature, the ambient magnetic field enters the thin films in the form of flux vortices and thermally activated movement of these vortices generates magnetic flux noise that can obscure the tiny magnetic signal generated, for example, by the human heart.

The researchers have eliminated this source of intrinsic noise for single-layer SQUIDs and magnetometers by making the YBCO film narrower than the mean distance that would separate vortices in the film, thus creating conditions that are energetically unfavorable to vortices entering the film. In devices involving superconducting multilayers in which a coil is coupled to a SQUID, the perimeter of the SQUID body must be large enough to overlap all the turns of the coil. For these devices, the researchers fabricated SQUIDs with slots or holes so the width of each strip of film is narrower than the required distance. (See figure below.) The low-noise multilayer magnetometers fabricated using this technique offer high sensitivity, and have potential applications in medical procedures such as magnetocardiography and magnetoencephalography, which would no longer require expensive magnetically shielded rooms. Other potential applications are in geophysical studies such as magnetotellurics (MT) and controlled-source electromagnetics (CSEM), where it is essential to operate the magnetometers in an unshielded environment. For further information, contact Technology Transfer Dept., Lawrence Berkeley National Lab, 1 Cyclotron Road, MS 90-1070, Berkeley, CA 94720; telephone (510) 486- 6467; telefax (510) 486-6457; e-mail ttd@lbl.gov; Web site http://www.lbl.gov/Tech-Transfer.

Preliminary field-trial results have been reported by Conductus, Inc. recently, for its five cellular base stations enhanced by the ClearSite(TM) receiver front end subsystem using superconductive technology. The cellular operators, located in the Midwest and Southeast, report a marked difference in voice quality at both sites. Additionally, the system provides diagnostic capability packaged in compact form factors. The Midwest carrier aims to enhance the base station footprint after they complete a rollout of TMDA digital service during the first half of 1998. This carrier has recorded noticeable improvements in the existing analog voice quality. The Southeast carrier aims to use the technology as a way to enhance base station coverage for low power (0.6 Watt) handsets in their local area consisting of rolling hills and mountainous terrain, leading to coverage gaps and dropped calls. This carrier has reported more uniform coverage of cell site, fewer dropped calls, and better analog voice-quality improvements. For further information, contact Stephen M. Garrison, Marketing Manager, Conductus, Inc., 969 West Maude Ave., Sunnyvale, CA 94086; telephone (408) 523-9430; telefax (408) 523-9999.

Contributed by Sreeparna Mitra

(Please view figure in the Web version of the newsletter).

FIG. 1. Photomasks for three varieties of high-Tc SQUIDs (a) solid, (b) 8 slots, and (c) 248 slots. Carving slots or holes into a high-Tc SQUID solves the problem of intrinsic magnetic noise in an ambient magnetic field.

PREPRINTS To obtain a particular preprint, contact the first author at the address given at the end of the citation. Help us expand this list by sending us your complete preprint. Please specify where and when your paper was submitted. An * next to an entry indicates it is a correction or revision of a previous entry. PACS codes and/or key words are given at the end of the citation.

S. Adachi, A. Tokiwa-Yamamoto, A. Fukuoka, R. Usami, T. Tatsuki, Y. Moriwaki, and K. Tanabe, "Hg-Based Homologous Series Superconductors, Hg-12(n-1)n and (Hg,Tl)-22(n-1)n." Preprint #N97008; to be published in Studies of High Temp. Supercond., Vol. 23, edited by A. V. Narlikar (Nova Science Publishers). 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.

A. A. Aligia and E. R. Gagliano, "'Superconductor'-Insulator Transitions in a Hubbard Chain with Nearest-Neighbor and Bond-Charge Interactions." Submitted to Phys. Rev. Lett. Comision Nacional de Energia Atomica, Centro Atomico Bariloche and Instituto Balseiro, 8400 S.C. de Bariloche, ARGENTINA; e-mail aligia@cab.cnea.edu.ar. 74.20.Mn; 71.10.+x; 71.27.+a.

V.P.S. Awana, J. Horvat, S. X. Dou, A. Sedky, and A. V. Narlikar, "Impact of Pr on Structural, Superconducting and Magnetic Properties of Y1-xPrxBaSrCu3O7." To be published in J. Magn. & Magn. Mater. Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, AUSTRALIA; telephone +61 42 21 5770; telefax +61 42 21 5731; e-mail awana@uow.edu.au. Key words: RE-based high-Tc cuprates, Pr substitution, magnetic hybridization, pair breaking. 74.20.Mn; 74.25.- q; 74.62.Dh; 74.72.-h.

R. Balian, H. Flocard, and M. Veneroni, "Temperature Dependence of Even- Odd Effects in Small Superconducting Systems." Submitted to Phys. Rev. Lett. S.Ph.T, SEA, Saclay, F-91191 Gif sur Yvette Cedex, FRANCE; H. Flocard's e-mail flocard@ipno.in2p3.fr; preprint also available at cond- mat@xxx.lanl.gov (#9802006). 21.60.-n; 74.20.Fg; 74.25.Bt; 74.80.Fp.

Mourad Benakli, Enzo Granato, Subodh R. Shenoy, and Marc Gabay, "Diluted Josephson-Junction Arrays in a Magnetic Field: Phase Coherence and Vortex Glass Thresholds." To be published in Phys. Rev. B. Condensed Matter Physics Group, International Centre for Theoretical Physics, I- 34100 Trieste, ITALY; Enzo Granato's e-mail enzo@las.inpe.br; preprint also available at cond-mat@xxx.lanl.gov (#9802032). 74.50.+r; 74.60.Ge; 64.60.Cn.

C. Bergemann, A. W. Tyler, A. P. Mackenzie, J. R. Cooper, S. R. Julian, and D. E. Farrell, "Superconducting Magnetization Above the Irreversibility Line in Tl2Ba2CuO6+d." Submitted to Phys. Rev. B. Low Temperature Physics Group, Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UNITED KINGDOM; telephone +44 1223 337351; telefax +44 1223 363263; e-mail cb203@cus.cam.ac.uk; preprint also available at cond-mat@xxx.lanl.gov (#9801278). 74.25.Ha; 74.60.Ec; 74.72.Fq; 07.55.Jg.

S. D. Berger and B. I. Halperin, "Parity Effect in a Small Superconducting Particle." Department of Physics, Harvard University, Cambridge, MA 02138; e-mail berger@cmt.harvard.edu; preprint also available at cond-mat@xxx.lanl.gov (#9801286).

C. Bernhard, Ch. Niedermayer, T. Blasius, G.V.M. Williams, R. De Renzi, C. Bucci, and J. L. Tallon, "A Muon Spin Rotation Study of Zn- and Ni- Impurity Related Magnetic Moments in Cuprate High-Tc Superconductors." Submitted to Phys. Rev. B. Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; telephone +49 711 689 1733; telefax +49 711 689 1010; e-mail bernhard@cardix.mpi-stuttgart.mpg.de. 74.62.-Dh; 74.25.Nf; 76.75.+i.

Antonio Bianconi, Antonio Valletta, Andrea Perali, and Naurang L. Saini, "Electronic Structure and Superconductivity of a Striped Phase at the Atomic Limit." To be published in Physica C (in press). Dipartimento di Fisica, Universita di Roma 'La Sapienza', P. Aldo Moro 5, I-00185 Roma, ITALY; telephone +39 6 499 14405; telefax +39 6 495 7697; e-mail antonio.bianconi@roma1.infn.it

K. Biedermann, A. Chrestin, T. Matsuyama, and U. Merkt, "Magnetic-Field Dependence of Fiske Resonances in Nb/P-Type InAs/Nb Weak Links." To be published in Appl. Supercond. Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, D-20355 Hamburg, GERMANY.

Howard A. Blackstead and John D. Dow, "Self-Test of Spin-Fluctuation Pairing." Manuscript #G9043/B5074; to be published in Europhys. 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, spin fluctuations. 74.25.-q; 74.72.Jt; 74.20.De; 74.20.Mn.

H. Bucheli, O. S. Wagner, V. B. Geshkenbein, A. I. Larkin, and G. Blatter, "(4+N)-Dimensional Elastic Manifolds in Random Media: A Renormalization-Group Analysis." Preprint #ETH-TH/97-33; to be published in Phys. Rev. B. Theoretische Physik, ETH-Hoenggerberg, CH- 8093 Zurich, SWITZERLAND; O. S. Wagner's e-mail orlando@itp.phys.ethz.ch; preprint also available at cond- mat@xxx.lanl.gov (#9801036).

C. P. Burgess, J. M. Cline, and C. A. Luetken, "Electromagnetic Response and Approximate SO(5) Symmetry in High-Tc Superconductors." Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, CANADA H3A 2T8; J. M. Cline's e-mail jcline@hep.physics.mcgill.ca; preprint also available at cond-mat@xxx.lanl.gov (#9801303). 78.30.-j; 72.20.-i; 74.72.-h.

P. Burlet, J. Y. Henry, and L. P. Regnault, "In-Plane Magnetic Anisotropy in Antiferromagnetic YBa2Cu3O6+x." To be published in Physica C (in press). CEA, Departement de Recherche Fondamentale sur la Matiere Condensee, SPSMS-MDN, 17 Rue des Martyrs, F-38054 Grenoble Cedex 9, FRANCE; telephone +33 476 884126; telefax +33 476 885109; e-mail burlet@drfmc.ceng.cea.fr. Key words: high-Tc cuprates, magnetic structure, magnetic anisotropy.

E. Cappelluti, C. Grimaldi, and L. Pietronero, "Role of the Superconducting Gap Opening on Vertex Corrections." Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; telephone +49 711 689 1537; telefax +49 711 689 1595; e-mail emmcapp@audrey2.mpi-stuttgart.mpg.de; preprint also available at cond- mat@xxx.lanl.gov (#9801232). 74.25.-q; 63.20.Kr; 71.38.+i.

H. Deng, C. Dong, Y. R. Zhou, F. Wu, H. Chen, S. L. Jia, J. C. Shen, G. S. Yuan, and Z. X. Zhao, "Ca Doped YBaSrCu2.5B0.5-xSxOz Series: Combination Effect of the Cation and Oxyanion Doping." To be published in Physica C (in press). Contact C. Dong, National Laboratory for Superconductivity, Institute of Physics, Academia Sinica, Beijing 100080, PEOPLE'S REPUBLIC OF CHINA; telephone +89 106 255 9131; telefax +86 106 256 8834. Key words: calcium doping, sulphur doping, substitution effects, Y(BaSr)2Cu2.5B0.5Oz, superconductivity.

J. C. Gallop, L. Hao, and R. P. Reed, "The Quantum Roulette Noise Thermometer." To be published in Applied Supercond. (in press). Centre for Basic and Thermal Metrology, National Physical Laboratory, Teddington TW11 0LW, UNITED KINGDOM.

W. Goeb, W. Lang, and Roman Sobolewski, "Magnetoresistance of a YBa2Cu3O7 Corbino Disk: Probing Geometrical Contributions to the Unconventional Normal-State Magnetoresistance of High-Temperature Superconductors." To be published in Phys. Rev. B. Contact W. Lang, Ludwig Boltzmann Institut fuer Festkoerperphysik, Kopernikusgasse 15, A- 1060 Wien, AUSTRIA; telephone +43 1 586 3408 21; telefax +43 1 586 3408 13; e-mail wolfgang.lang@univie.ac.at. 74.72.Bk; 74.76.Bz; 72.15.Gd; 74.40.+k.

D. A. Gorokhov and G. Blatter, "Quantum Depinning of a Pancake-Vortex from a Columnar Defect." Preprint #ETH-TH/97-22; to be published in Phys. Rev. B. Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich, SWITZERLAND; D. A. Gorokhov's e-mail gorokhov@itp.phys.ethz.ch; preprint also available at cond-mat@xxx.lanl.gov (#9802016). 64.60.My; 74.50.+r; 74.60.Ge.

D. A. Gorokhov and G. Blatter, "Thermally Activated Hall Creep of Flux Lines from a Columnar Defect." Preprint #ETH-TH/97-20; to be published in Phys. Rev. B. Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich, SWITZERLAND; D. A. Gorokhov's e-mail gorokhov@itp.phys.ethz.ch; preprint also available at cond-mat@xxx.lanl.gov (#9802015). 64.60.My; 74.50.+r; 74.60.Ge.

B. Grevin, Y. Berthier, G. Collin, and P. Mendels, "Evidence for Charge Instability in the CuO3 Chains of PrBa2Cu3O7 from [63,65]^Cu NMR." To be published in Phys. Rev. Lett. Laboratoire de Spectrometrie Physique, UMR 5588 CNRS, Universite Joseph Fourier Grenoble I, BP 87, F-38402 Saint-Martin d'Heres Cedex, FRANCE. 71.45.Lr; 74.72.Jt; 76.60.-k; 76.60.Gv.

L. Hao, J. C. Gallop, R. P. Reed, J. C. MacFarlane, and E. Romans, "Shunted YBCO Bicrystal Junctions for Noise Thermometry." To be published in Applied Supercond. (in press). Centre for Quantum Metrology, National Physical Laboratory, Teddington TW11 0LW, UNITED KINGDOM.

S. K. Hasanain, Shaista Shahzada, and A. Mumtaz, "Magnetization Dynamics in Crossed ac and dc Fields." To be published in Physica C (in press). Department of Physics, Quaid-i-Azam University, Islamabad 45320, PAKISTAN; telephone +92 51 82 9472; telefax +92 51 21 0256; e-mail hasanain@physics.sdnpk.undp.org. Key words: cross flux, swept mode, relaxation.

S. Hebert, V. Hardy, G. Villard, M. Hervieu, Ch. Simon, and J. Provost, "Pinning Enhancement in Bi2Sr2CaCu2O8 by Tilting Columnar Defects from the c Axis." To be published in Physica C. Laboratoire CRISMAT, UMR 6508, ISMRA et Universite de Caen, 6 Boulevard du Marechal Juin, F-14050 Caen Cedex, FRANCE. Key words: critical current density, irreversibility line, irradiation effect, columnar defects.

W. Henderson and E. Y. Andrei, "Plastic Flow of a Magnetic Flux-Line Lattice." Submitted to Nature. Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08855.

N. E. Hussey, M. Kibune, H. Nakagawa, N. Miura, Y. Iye, H. Takagi, S. Adachi, and K. Tanabe, "Magnetic Field Induced Dimensional Crossover in the Normal State of YBa2Cu4O8." Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106, JAPAN; telephone +81 3 3478 6811, ext. 5663; telefax +81 3 3478 7698; e-mail nehussey@troy.issp.u-tokyo.ac.jp. 74.25.Fy; 74.70.Kn; 74.72.Bk.

T. A. Jacobson and G. E. Volovik, "Event Horizons and Ergoregions in [3]^He." Department of Physics, University of Maryland, College Park, MD 20742-4111; preprint also available at cond-mat@xxx.lanl.gov (#9801308).

Q. X. Jia, A. T. Findikoglu, P. Arendt, S. R. Foltyn, J. M. Roper, J. R. Groves, J. Y. Coulter, Y. Q. Li, and G. F. Dionne, "Superconducting YBa2Cu3O7-x Thin Films on Polycrystalline Ferrite for Magnetically Tunable Microwave Components." Preprint #LA-UR-98-553; to be published in Appl. Phys. Lett. Superconductivity Technology Center, Los Alamos National Laboratory, Mail Stop K763, Los Alamos, NM 87545; telephone (505) 667-2716; telefax (505) 665-3164; e-mail qxjia@lanl.gov.

M. Kawano, H. Suematsu, T. Onda, M. Hayakawa, M. Karppinen, H. Ogiwara, and H. Yamauchi, "Peak Effect in Jc of the Cation-Stoichiometric SmBa2Cu3Oy Superconductor." To be published in Appl. Supercond. Contact H. Yamauchi, Materials & Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, JAPAN; telephone +81 45 924 5315; telefax +81 45 921 6953; e-mail yamauchi@materia.titech.ac.jp. Key words: stoichiometric SmBa2Cu3Oy, peak effect, oxygen content.

G. J. Kaye, "Interpretation of the ARPES Normal State Gap in Cuprate Superconductors from a Mixed-Boson-Fermion Model." To be published in Physica C (in press). IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UNITED KINGDOM. Key words: cuprate superconductors, angle-resolved photoemission, normal- state gap, polarons and bipolarons.

R. A. Klemm, C. T. Rieck, and K. Scharnberg, "Angular Dependence of the Josephson Critical Current in c-Axis Twist Junctions of High Temperature Superconductors." Submitted to Phys. Rev. B. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov.

E. Kochetov, V. Yarunin, and M. Zhuravlev, "Adiabatic Approximation for Localized Electrons in Periodic Anderson Model." To be published in Physica C (in press). Contact V. Yarunin, Bogolubov Theoretical Laboratory, Joint Institute for Nuclear Research, Dubna 141980, RUSSIA; telefax +7 09621 65084; e-mail yarunin@thsun1.jinr.dubna.su. Key words: Anderson lattice, band structure, Hubbard variables, SU(2|1) coherent states.

M. Krusius, T. Vachaspati, and G. E. Volovik, "Flow Instability in [3]^He-A as Analog of Generation of Hypermagnetic Field in Early Universe." Low Temperature Laboratory, Helsinki University of Technology, 02015 Espoo, FINLAND; preprint also available at cond- mat@xxx.lanl.gov (#9802005).

M. Kund, J. J. Neumeier, K. Andres, J. Markl, and G. Saemann-Ischenko, "Large Anisotropic Pressure Effects in Electron-Doped Sm2-xCexCuO4-y." To be published in Physica C (in press). Contact J. J. Neumeier, Department of Physics, Florida Atlantic University, Boca Raton, FL 33431; telephone (561) 367-3380; telefax (561) 367-2662; e-mail physics@fau.edu. Key words: thermal expansion, high pressure, anisotropy, single crystal, Sm2-xCexCuO4-y. 74.72.-h; 65.70.+y; 74.62.Fj.

K. Kwasnitza, St. Clerc, R. Fluekiger, and Y. B. Huang, "Alternating Magnetic Field Losses in High-Tc Superconducting Multifilament Tapes with a Mixed Matrix of Ag and BaZrO3." To be published in Physica C. Paul Scherrer Institut, CH-5232 Villigen PSI, SWITZERLAND; telephone +41 56 310-3593 or -2111; telefax +41 56 310-3294. Key words: ac losses, Bi-2223 high-Tc superconducting multifilament tapes, Ag-Ba-ZrO3 mixed matrix.

M. M. Leivo, A. J. Manninen, and J. P. Pekola, "Microrefrigeration by Normal-Metal/Insulator/Superconductor Tunnel Junctions." To be published in Appl. Supercond. Department of Physics, University of Jyvaeskylae, P.O. Box 35, FIN-40351 Jyvaeskylae, FINLAND.

J. Lesueur, B. Leridon, M. Aprili, and X. Grison, "Tunneling in High-Tc Superconducting Cuprates." Submitted to the Proc. of the NATO Adv. Study Inst. on the Gap Symmetry and Fluctuations in High-Tc Supercond., Inst. d'Etudes Scientifiques de Cargese, Corsica, France, Sept. 1-12, 1997. C.S.N.S.M., Batiment 108, Universite Paris-Sud, F-91405 Orsay Cedex, FRANCE; telephone +33 1 6915 5231; telefax +33 1 6915 5268; e- mail lesueur@csnsm.in2p3.fr. Key words: superconductivity, tunneling, Josephson effect, order parameter, density of states, gap.

F. Letouze, M. Hervieu, C. Martin, A. Maignan, and B. Raveau, "Local Ordering of the Chromate Groups in the '1212' Superconductor Tl0.9(CrO4)0.2Sr2Ca0.9Cu2O6.2-d." To be published in Physica C (in press). Contact C. Martin, Laboratoire CRISMAT, UMR 6508 associee au CNRS, ISMRA, Universite de Caen, 6 Boulevard du Marechal Juin, F-14050 Caen Cedex, FRANCE; e-mail martin@crismat.ismra.fr. Key words: thallium superconductor, synthesis, HREM, superconductivity. 74.72.Fq; 61.16.Bg; 74.25.Ha.

Z. W. Lin, J. W. Cochrane, G. J. Russell, S. X. Dou, and H. K. Liu, "Visualization of Magnetic Flux Distribution in Bi(Pb)-2223/Ag Multifilamentary Tapes." Advanced Electronic Materials Group, School of Physics, University of New South Wales, Sydney NSW 2052, AUSTRALIA; e- mail lzw@newt.phys.unsw.edu.au.

F. Ludwig, J. Beyer, D. Drung, S. Bechstein, and Th. Schurig, "YBa2Cu3O7-x dc SQUID Magnetometers with Bicrystal Junctions for Biomagnetic Multichannel Applications." To be published in Appl. Supercond: Proc. of the 6th Int. Supercond. Electronics Conf. (ISEC'97), Berlin, Germany, June 26-28, 1997. Physikalisch-Technische Bundesanstalt, Institut Berlin, Abbestrasse 2-12, D-10587 Berlin, GERMANY; telephone +49 30 3481 434; telefax +49 30 3481 490.

I. L. Maksimov and A. A. Elistratov, "Magnetization Curves and Hysteretic Losses in Superconducting Films with Edge Barrier." Submitted to Appl. Phys. Lett. Department of Applied Physics and Microelectronics, Nizhny Novgorod University, 23 Gagarin Ave., Nizhny Novgorod 603000, RUSSIA; telephone +7 831 2 65 6255; telefax +7 831 2 35 6480 (Box 108); e-mail ilmaks@phys.unn.runnet.ru.

R. S. Markiewicz and C. Kusko, "Tunneling Studies of Pseudogaps: A Comment." Submitted to Phys. Rev. Lett. 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 (#9802079).

R. S. Markiewicz and M. T. Vaughn, "The Spectrum-Generating Algebra of the Van Hove Scenario is SO(8)." Submitted to Phys. Rev. B. 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 (#9802078).

R. S. Markiewicz and M. T. Vaughn, "Stripes, Pseudogaps, and SO(6) in the Cuprate Superconductors." To be published in J. Phys. Chem. Solids: Proc. of the Conf. on Spectroscopies in Novel Supercond. (SNS'97), Cape Cod, Mass., Sept. 14-18, 1997. 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 (#9709137).

V. Meregalli and S. Y. Savrasov, "Is Doped BaBiO3 a Conventional Superconductor?" Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, GERMANY; e-mail valeria@and.mpi- stuttgart.mpg.de; preprint also available at cond-mat@xxx.lanl.gov (#9801251).

Th. Muehge, N. N. Garif'yanov, Yu. V. Goryunov, K. Theis-Broehl, K. Westerholt, I. A. Garifullin, and H. Zabel, "Influence of Superconductivity on Magnetic Properties of Superconductor/Ferromagnet Epitaxial Bilayers." To be published in Physica C (in press). Institut fuer Experimentalphysik/Festkoerperphysik, Ruhr-Universitaet Bochum, D- 44780 Bochum, GERMANY; telephone +49 234 700 3632; telefax +49 234 709 4173; e-mail thosten.muehge@rz.ruhr-uni-bochum.de. Key words: multilayers, thin films, proximity effect.

H. Okamura, S. Nagaya, H. Suematsu, and H. Yamauchi, "Peak Effect in Jc and Sub-Micron Structures of Y-Ba-Cu-O Superconducting Bulks Melt-Grown Under Varying Oxygen Pressure." To be published in Appl. Supercond. Contact H. Yamauchi, Materials & Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, JAPAN; telephone +81 45 924 5315; telefax +81 45 921 6953; e-mail yamauchi@materia.titech.ac.jp. Key words: peak effect, Y-Ba-Cu-O superconductors, large area TEM observation, FIB thinned TEM specimens, statistical analysis, twin boundaries.

P. V. Patanjali, V. Seshu Bai, R. M. Kadam, and M. D. Sastry, "Anomalous Microwave Absorption in GdBCO Powder: pi Junctions and the Paramagnetic Meissner Effect." To be published in Physica C (in press). School of Physics, University of Hyderabad, Hyderabad 500 046, INDIA; telephone +91 22 215 2971; telefax +91 22 215 2110; e-mail pat@tifrc3.tifr.res.in. Key words: microwave absorption, Meissner effect, pi junction.

X. G. Qiu, V. V. Moshchalkov, Y. Bruynseraede, and J. Karpinski, "Vortex Lattice Melting into Disentangled Liquid Followed by the 3D-2D Decoupling Transition in YBa2Cu4O8 Single Crystals." Submitted to Phys. Rev. Lett. Research Laboratory for Engineering Materials, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226, JAPAN; telefax +81 45 924 5360. 74.60.Ge; 74.25.Fy; 74.72.Bk.

E. Rodriguez, A. Gou, B. Martinez, S. Pinol, and X. Obradors, "Influence of Disorder on the Vortex Lattice Melting in Twinned, Oxygen-Deficient Ortho-II YBa2Cu3Oy (y~~6.6)." To be published in Phys. Rev. B. Laboratorio de Bajas Temperaturas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Buenos Aires, Ciudad Universitaria, Pab. I, 1428 Buenos Aires, ARGENTINA; e-mail eduardo@df.uba.ar. 74.60.Ge.

P. Romano, A. M. Cucolo, R. Di Leo, E. Bacca, and P. Prieto, "Conductance Characteristics of BiSrCaCuO-Based Trilayer Structures." To be published in Physica C (in press). Unita INFM, Dipartimento di Fisica, Universita di Salerno, I-84081 Baronissi (Sa), ITALY; telephone +39 89 965376; telefax +39 89 953804; e-mail rmano@vaxsa.csied.unisa.it.

K. Salama and S. Sathyamurthy, "Recent Developments in Melt Texturing of 123 Compounds." Preprint #98:019; submitted to the Proc. of the Int. Symp. on Processing and Critical Currents of HTS, Wagga Wagga, Australia, Feb. 2-4, 1998. 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.

F. M. Sauerzopf, "Anisotropic Flux Pinning in YBa2Cu3O7-d Single Crystals: The Influence of Defect Size and Density as Determined from Neutron Irradiation." To be published in Phys. Rev. B. Atominstitut der OEsterreichischen Universitaeten, A-1020 Vienna, AUSTRIA.

G. J. Schmitz, J. C. Schmidt, M. Tarka, and A. Tigges, "Texturing of (RE)BaCuO Thick Films by Geometrical Arrangement of Reactive Precursors." To be published in Supercond. Sci. & Technol.: Proc. of the Int. Symp. on Processing and Critical Currents of HTS, Wagga Wagga, Australia, Feb. 2-4, 1998. Materialforschung, ACCESS e.V., Intzestrasse 5, D-52072 Aachen, GERMANY; telephone +49 241 806721; telefax +49 241 38578; e-mail gjs@gi.rwth-aachen.de.

R. Seviour, C. J. Lambert, and M. Leadbeater, "Large-Scale Superconductivity-Induced Conductance Suppression in Mesoscopic Normal- Superconducting Structures." School of Physics and Chemistry, Lancaster University, Lancaster LA1 4YB, UNITED KINGDOM; telephone +44 1524 65201; telefax +44 1524 844037; e-mail physics@lancaster.ac.uk; preprint also available at cond-mat@xxx.lanl.gov (#9712166). 74.25.Fy; 73.23.-b; 72.10.-d.

C. Stockinger, W. Markowitsch, W. Lang, W. Kula, and Roman Sobolewski, "Mechanisms of Photodoping in Oxygen-Deficient YBa2Cu3Ox Films Studied by In-Situ Transport Measurements." To be published in Phys. Rev. B. Contact W. Markowitsch, Ludwig Boltzmann Institut fuer Festkoerperphysik, Kopernikusgasse 15, A-1060 Wien, AUSTRIA; telephone +43 1 586 3408 20; telefax +43 1 586 3408 13; e-mail wilhelm.markowitsch@univie.ac.at. 73.50.Jt; 73.50.Pz; 74.72.Bk; 74.76.Bz.

T. Tamura, S. Adachi, X.-J. Wu, T. Tatsuki, and K. Tanabe, "Pb-Based Cuprate Superconductor with the 1234 Structure Synthesized Using a High- Pressure Technique." Preprint #N97300; to be published in Physica C. 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 3536-5717.

F. Warmont, V. Hardy, J. Provost, D. Grebille, and Ch. Simon, "Electronic Anisotropy of the Superconducting (Tl2/3,Bi1/3)Sr2CaCu2Ox Compound Measured by Angular Resolved Magnetoresistivity." To be published in Phys. Rev. B. Laboratoire CRISMAT, CNRS UMR 6508, ISMRA, 6 Boulevard du Marechal Juin, F-14050 Caen Cedex, FRANCE. 74.72.-h

Carsten Wengel and Uwe Claus Taeuber, "Properties of the Bose Glass Phase in Irradiated Superconductors near the Matching Field." Institut fuer Theoretische Physik, Universitaet Goettingen, Bunsenstrasse 9, D- 37073 Goettingen, GERMANY; Uwe Claus Taeuber's telephone +49 89 289 12356; telefax +49 89 289 12296; e-mail utaeuber@physik.tu-muenchen.de; preprint also available at cond-mat@xxx.lanl.gov (#9801264). 74.60.Ge; 05.60.+w.

M. E. Zhitomirsky and M. B. Walker, "Effect of Spatial Variations of Superconducting Gap on Suppression of the Transition Temperature by Impurities." 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 (#9802055). 74.20.Fg; 74.62.Dh; 74.72.-h.

COMING EVENTS (An * indicates a previously listed event.)

May 12 - 13, 1998: Pulsed Laser Deposition Technological Barriers -- Research Needs and Opportunities, Holiday Inn Arlington at Ballston, Va. Hosted by National Institute of Standards and Technology (NIST) and Naval Research Laboratory (NRL). Purpose is to examine technological barriers that may be limiting the wider application of PLD. Some issues include: scale-up; particulate control; development of process measurement and control protocols; and issues concerned with film quality including stoichiometry, epitaxy, and structure. Leading representatives from industry, federally funded laboratories, and academia will discuss techniques, problems, and future directions of PLD. Representatives from government research-directing agencies such as NSF, ONR, DARPA, DOE, and others will be present for discussion of research issues and support for pre-commercial efforts. Workshop format will consist of series of discussions that begin with short presentations by the discussion leaders. Discussion topics will include: technical barriers; the perceived role for NIST, DOD, national laboratories, NSF-universities, and industry; and strengths and weaknesses of PLD for its development as a practical commercial process. Workshop proceedings volume is planned. Registration deadline, April 3, 1998. Registration fee $100. For information, contact Kathy Jackson, Naval Research Laboratory, telephone (202) 404-2085; e-mail kjackson@ccf.nrl.navy.mil; Web site http://amp.nrl.navy.mil/code6670/workshop.html.

*June 7 - 12, 1998: European Conference on Energy Dispersive X-ray Spectrometry 1998 (EDXRS-98), Aula Prodi, San Giovanni in Monte, Bologna, Italy. Aim is to bring together experts and users of energy dispersive x-ray spectrometry working either in basic research in x-ray spectrometry, detectors and sources, or applications of x-ray spectrometry. Topics are: interactions of x-rays with matter and their modeling, special applications of polarized radiation, conventional techniques, advances in x-ray spectrometry, data handling and instrumentation, energy dispersive x-ray detectors, microanalysis with photon sources, microanalysis with charged particles, x-ray optics, TXRF and capillarity, and specific applications. Abstract deadline, March 15, 1998. Official language is English. Selected papers will be printed in a special issue of the International Journal of X-Ray Spectrometry. For information, contact Barbara Cavallari, Organizing Secretariat, Laboratario delle IDEE Srl, Via S. Stefano 32, I-40125 Bologna, Italy; telephone +39 51 261440; telefax +39 51 265742; Web site http://www.ing.unibo.it/Eventi/edxrs98/welcome.html.

#July 12 - 15, 1998: 1998 International Workshop on Superconductivity: Materials and Technology Issues for HTS Wires and Bulk Applications, Okinawa Harborview Hotel, Naha-shi, Okinawa, Japan. Workshop will focus on high-temperature superconductors in all forms. Topics of interest are: physics and characterization of HTS bulks, wires, and tapes; crystal growth and processing of HTS bulks, wires, and tapes; applications; flux pinning and flux dynamics; ac losses; and novel materials. A significant amount of time will be allotted for discussion of each paper, and extra time will be set aside for informal interactions among the participants. No parallel sessions. For information, contact Kiyomi Funakoshi, Workshop Secretary, Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), Eishin Kaihatsu Bldg., 6F, 34-3, Shinbashi 5- chome, Minato-ku, Tokyo 105-0004, Japan; telephone +81 3 3431 4002; telefax +81 3 3431 4044; e-mail funa@istec.or.jp. #Note corrected postal address.

*July 19 - 24, 1998: Superconducting Superlattices II -- Native and Artificial: Symposium SD81 of the SPIE's Annual Meeting on Optical Science, Engineering, and Instrumentation, San Diego Convention Center and the Marriott Hotel & Marina, San Diego, Calif. Conference will include papers devoted to structural, electronic, transport, and other phenomena in such heterostructures and inter-calates. Experimental and theoretical papers which are related to superconducting superlattices are solicited in the following areas: (1) epitaxial and morphological properties, interface smoothness and disorder, layer thickness fluctuations, interdiffusion, and strain, structure of defects; (2) critical temperature, critical currents, and critical magnetic fields; (3) nature of c-axis transport in cuprates and artificial superlattices; (4) electronic structure, charge redistribution, localization, single- particle and collective excitations; 5) Josephson phenomena in natural and artificial superlattices and Josephson plasma oscillations; (6) structure of flux lines, thermal and field-induced flux motion, intrinsic flux pinning; (7) effective dimensionality and dimensional crossovers, superconductivity in ultrathin layers, Kosterlitz-Thouless transition; and (8) proximity effects: superconductors in contact with insulators, semiconductors, normal metals, ferro- and antiferromagnets, piezoelectrics, etc. Proceedings to be published. For information, contact SPIE, P.O. Box 10, Bellingham, WA 98225; telephone (360) 676- 3290; telefax (360) 647-1445; e-mail SD98@spie.org; Web site http://www.spie.org.

*July 19 - 24, 1998: Superconducting and Related Oxides: Physics and Nanoengineering III, Symposium SD82, is third in the series of SPIE conferences focused on basic issues in physics and materials science of high-temperature superconductors and related compounds that may be relevant for their applications in electronics, optics, and optoelectronics. Venue is the same as in the previous listing. Scientists and engineers engaged in research on superconducting materials and related compounds, as well as their novel applications, are invited to participate. Original papers are solicited on, but not limited to, the following topics: (1) structural, transport, magnetic, and thermal properties of thin films of cuprates and related compounds; (2) homoepitaxy and new substrate materials; (3) search for novel high- temperature superconducting phases by atomic engineering; (4) composition and structure of defects; (5) anion and cation substitutions, metal-insulator transition, and localization; (6) proximity effects; surface and interface effects; superconductors in contact with insulators, semiconductors, normal metals, ferro- and antiferromagnets, piezoelectrics, etc.; (7) novel device concepts, electric field effect in heterostructures, hybrid optoelectronic devices, and cryo-electronics. A round-table discussion is planned in which representatives of prominent groups in industry, academia, and national laboratories will be invited to expound on their respective progress and strategies in combining basic physics and materials research and developing specific applications, and discuss the future of superconducting electronics. Proceedings to be published. For information, contact SPIE, P.O. Box 10, Bellingham, WA 98225; telephone (360) 676-3290; telefax (360) 647-1445; e-mail SD98@spie.org; Web site http://www.spie.org.

*July 26 - Aug. 8, 1998: NATO Advanced Study Institute -- Physics and Materials Sciences of the Vortex States, Flux Pinning, and Dynamics, Kusadasi, Turkey. Topics include statistical mechanical vortex lines, phase transitions in vortex ensemble, critical currents and microstructure, magnetic flux penetration and vortex dynamics in HTSC films, pinning mechanisms in high-temperature superconductors, magneto- optical study of flux penetration, statistics and dynamics of flux-line lattice in realistic geometries, vortex statics and dissipation-related properties in layered HTSC, practical issues of flux pinning and vortex dynamics for HTS materials, static and dynamic vortex states, Josephson vortex dynamics in layered structures, relevance of flux pinning and dynamics to engineering applications of high-temperature superconductors, and flux distribution instabilities in a current- carrying state of type-II superconductors. Application deadline, March 1, 1998. For information, contact Ram Kossowsky, ETI, 6327 Burchfield Avenue, Pittsburgh, PA 15217; telephone (412) 421-4408; telefax (412) 421-4342; e-mail ramkoss@mindspring.com.

July 27 - Sept 18, 1998: Extended Research Workshop on Disorder, Chaos and Interaction in Mesoscopic Systems, International Centre for Theoretical Physics, Trieste, Italy. Workshop aims to bring together the key researchers from both developed and developing countries and young people working in the field, to benefit from the common research work, informal discussions, and interactions. No formal talks or conferences planned; the aim is to concentrate on research rather than on presentations. Topics include Anderson localization, mesoscopic fluctuations, semiclassical approximation in chaotic systems, interactions in quantum dots, dephasing in mesoscopic systems, application of field theory to quantum chaos, numerical simulations in disordered and chaotic systems, and random matrix theory. Scientists and students from all countries that are members of the UN, UNESCO, or IAEA can attend the Workshop. Workshop will be conducted in English. Deadline for requesting participation in the Workshop with financial support, March 31, 1998; deadline for participation request without financial support, April 30, 1998. Contact Extended Research Workshop on Disorder, Chaos and Interaction in Mesoscopic Systems, International Centre for Theoretical Physics, P.O. Box 586, I-34100 Trieste, Italy; Web site http://www.ictp.trieste.it.

*Sept. 13 - 18, 1998: The 1998 Applied Superconductivity Conference (ASC), Marriott's Desert Springs Resort, Palm Desert, Calif. Conference encourages contributed papers in three major areas of applied superconductivity: electronics, materials, and large-scale applications. For 1998, the theme Superconductivity -- Coming to Market, will be developed through a series of plenary and invited talks. Abstracts are solicited for papers that show a clear connection to applied superconductivity. Abstract deadline, March 9, 1998; abstract deadline for submission via the ASC Web site, March 16, 1998. Selected papers will be published in IEEE Transactions on Appl. Supercond. For information about the conference and programs for companions, contact Centennial Conferences, 4800 Baseline Rd., A-112, Boulder, CO 80303; telephone (303) 499-2299; telefax (303) 499-2599; e-mail centennial@orci.com; Web site www.ascinc.org. For submission of abstracts or technical information, contact Ron Scanlan, Applied Superconductivity Conference, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., MS 46-161, Berkeley, CA 94720; telephone (510) 486-7241; telefax (510) 486-5310; e-mail rmscanlan@lbl.gov.

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Position open: A postdoctoral fellowship is available at the Department of Applied Physics at University of Linz (Austria) for HTS thin-film preparation and optimization. The project will involve experimental investigations (pulsed-laser deposition, XRD, AFM, and characterization of HTSC properties) to achieve high critical current densities. The position will be financed by an European Project on Technical Superconductors for Practical Applications. Citizens of European Union member states are eligible to apply. Interested candidates should send a curriculum vitae to Johannes Pedarnig, Department of Applied Physics, University of Linz, A-4040 Linz, Austria; e-mail johannes. pedarnig@jk.uni-linz..ac.at.

Position open: Applications are invited for a postdoctoral position in the field of colossal magneto-resistance material research. Applicants should have a good expertise in one or more of the following disciplines: crystal growth, characterization of single crystals by XRD, neutrons, and electrical and magnetic measurements. The selected candidate will join a seven-member European TMR research team supported by EC funds. Work will be performed at the University of Paris-Sud, Orsay, France. Due to the specific nature of the funding for this project, this position is open to applicants of European nationality but non-French. Send bio-data to A. Revcolevschi, Laboratoire de Chimie des Solides, Bat. 414 Universite Paris-Sud, F-91405 Orsay Cedex, France; telephone +33 1 69 15 70 18; telefax +33 1 69 15 47 97; e-mail revco@chimsol.u-psud.fr. Or contact J. P. Renard, Institut d'Electonique Fondamentale, Bat. 220, Universite Paris-Sud, F-91405 Orsay Cedex, France; telephone +33 1 69 15 40 77; telefax +33 1 69 15 40 00; e-mail Jean-Pierre.Renard@ief.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. 12, #5, March 1, 1998.