HIGH-Tc UPDATE E-MAIL VERSION, VOL. 12, NO. 8, April 15, 1998.

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:

Josephson Vortices

The interlayer Josephson vortices emerging from the ac face of single crystals of the single-layer cuprate high-Tc superconductor (Hg,Cu)Ba2CuO4+d have been imaged by J. R. Kirtley (IBM-Yorktown) et al. using a scanning SQUID microscope. The images provide a direct measurement of the c-axis penetration depth, lambda_c ~ 10 micrometers. This length is a factor of 10 larger than predicted by the interlayer tunneling (ILT) model for the mechanism of superconductivity in layered compounds [S. Chakravarty et al., Science 261, 337 (1993); P. W. Anderson, Science 268, 1154 (1995)], indicating that the condensation energy available through this mechanism is 100 times smaller than is required for superconductivity.

Intrinsic pinning of Josephson vortices in Bi2Sr2CaCu2O8+d has been studied by H. Haneda (Kyoto) et al. via measurements of the mutual conversion between ultrasonic waves and electromagnetic waves. From the dependence of this effect upon the angle of the applied magnetic field relative to the CuO2 planes, the authors observe a crossover from intrinsic pinning to pancake pinning.

The equilibrium magnetization for layered superconducting films that experience a nonzero component H_|| of magnetic field applied parallel to the layers has been computed by J. P. Rodriguez (Madrid and Cal State - Los Angeles) at temperatures and magnetic fields near the decoupling transition. The author finds that the parallel magnetization has an anomalous H_||^[-1] tail at high fields due to entropic fluctuations of the lattice of Josephson vortices.

More Vortices

An extensive numerical study of vortex matter has been carried out by H. Nordborg (ETH-Zurich and Argonne) and G. Blatter (ETH-Zurich) using the mapping to 2D bosons and path-integral Monte Carlo simulations. The authors find a first-order vortex-lattice melting transition into an entangled vortex liquid. The jumps in entropy and density are consistent with experimental results on YBa2Cu3O7-d. The liquid is denser than the solid. In the language of bosons, the authors find a sharp quantum phase transition from a Wigner crystal to a superfluid, even in the case of logarithmic interaction.

The translational order in a three-dimensional vortex lattice pinned by hopping defects, such as oxygen vacancies, has been studied theoretically by E. M. Chudnovsky (CUNY Lehman College). The author finds that long-range order in the vortex lattice is restored as the thermal hopping rate increases. The author suggests that this phenomenon, which would be equivalent to a thermal depinning transition, may occur in the low-field, high-temperature part of the field- temperature phase diagram.

Pinning by splayed and columnar defects created by 3.9 GeV [197]^Au^[29+] ions has been investigated by W. K. Kwok (Argonne) et al. using transport measurements of vortex motion perpendicular and parallel to the splay plane in untwinned crystals of YBa2Cu3O7-d. The authors compare these results with those from a sample with parallel columnar defects parallel to the c axis, and they report extensive measurements of the temperature, field, and angular dependencies of the vortex liquid and solid states. The authors find that the irreversibility lines for pre- and post-irradiated splayed-defect samples cross at twice the matching field. The authors also determined the vortex liquid pinning energy for splayed and columnar defects and found that the barrier to vortex motion perpendicular to the splay plane is greater than that to motion parallel to the splay plane.

Closed-form results for the vortex inertial mass due to variation of the magnitude of the superconducting order parameter are presented by M. W. Coffey (Colorado) for an s-wave superconductor. Certain matrix elements that use approximate wave function solutions of the Bogoliubov-de Gennes equations are evaluated. The resulting analytic expressions characterize the inertial mass and the core polarizability, and are suitable for incorporation in the vortex mobility at zero temperature.

The interaction between a magnetized probe tip and a superconducting sample, the basis for the imaging technique of magnetic force microscopy (MFM), has been calculated by M. W. Coffey (Colorado). The first part of the paper addresses the force between the probe tip and a vortex in the superconductor. The second part of the paper describes an MFM measurement method for determining the penetration depth profile when lambda depends upon the distance z from the surface.

Flux Motion

Two preprints by E. H. Brandt (MPI-Stuttgart) report theoretical developments regarding flux motion in type-II superconductors. In one of these, the author shows how to calculate the current density J(r,t) and magnetic induction B(r,t) in a superconductor with arbitrary shape and material laws H(B,r) (equilibrium field) and E(J,B,r) (electric field caused by flux-line motion) when a magnetic field B_a(r,t) and a current are applied. The author then calculates the geometric edge barrier for flux penetration, the current density at the flux front, and the field of first flux entry B_[en] for superconducting strips of rectangular cross section in a perpendicular field. In the other preprint, Brandt calculates the complex ac susceptibility chi = chi' - ichi" for superconducting cylinders of radius a and length 2b in parallel or perpendicular magnetic field using the model E proportional to J^n. Results for chi' and chi" are shown for ohmic (n = 1) cylinders with various aspect ratios (b/a = 0, 0.01, 0.03, 0.1, 0.3, 1, 2, 3, 5, and 10) and for nonohmic (n = 3, 5, 11, and 51) cylinders with aspect ratio b/a = 1.

A preprint by M. Daeumling (TU-Denmark) reports numerical computations of the critical-state magnetic field and current distributions for a superconducting strip of infinite length but finite thickness and width carrying an ac transport current. The aspect ratio (width/thickness) was varied from 1 to 100, covering the range from square bars to thick films. The calculated power-loss exponents n (P proportional to I^n) were found to vary from roughly 3 for a square bar to about 4 in a highly aspected thin strip. In the thin-film case, the power-loss exponents are current-dependent because of the contribution to the loss caused by the component of the magnetic field parallel to the strip. The author also calculated the maximum magnetic fields that occur and found that they fall on a universal curve that depends only on the aspect ratio.

Curves of E vs. J (local electric field versus current density) in YBa2Cu3O7-d and Nd1.85Ce0.15CuO4-d single crystals have been measured by D. Giller et al. (Bar Ilan) using a miniature Hall-sensor array. Measurements in the field range corresponding to the anomalous magnetization peak reveal different E-J characteristics above and below the peak, indicating a crossover in the flux-creep mechanism. The authors expect this E-J behavior to be universal in all superconductors exhibiting the anomalous peak.

A reentrant behavior of the peak effect has been found by S. S. Banerjee (TIFR-Mumbai) et al. in a single crystal of the anisotropic superconductor 2H-NbSe2 via electrical transport and dc magnetization studies: when plotted in the H-T plane, H_p (the value of the field where the peak effect occurs) is double-valued for temperatures near Tc. The authors find that the upper (high-field) branch of the H_p vs. T curve is relatively unaffected by disorder, while the lower (low-field), reentrant branch of the curve is strongly affected by disorder.

RBa2Cu3O7-d

As reported by D. A. Wright et al. (UC-Berkeley and LBNL), the temperature (T) and magnetic field (H) dependencies of the specific heat of YBa2Cu3O7-d (YBCO) show a number of features predicted for d-wave pairing: a T^2 term for H = 0 and an H^[1/2]T term for H not equal to 0 and low T, with a crossover to a stronger T dependence at higher T. For all H and T, the authors find the results to be consistent with a recently proposed scaling relation. The observed values of the crossover parameter and the coefficients of the T^2 and H^[1/2]T terms are in good agreement with theoretical calculations.

Strong evidence for both spin-2 and spin-1/2 paramagnetic centers in YBa2Cu3O7-d has been found by J. P. Emerson et al. (UC-Berkeley and LBNL) in specific-heat data in the vicinity of 1 K. This work provides a basis for the determination of more reliable values for all parameters derived from low-temperature specific-heat data. The authors report the concentrations of both kinds of paramagnetic centers, Debye temperatures, and the coefficients of the T-proportional term for 0 <= d <= 0.2.

Copper isotope shifts of Tc have been measured by D. E. Morris et al. (Morris Research) in 123 and 124 cuprate superconductors with partial substitutions by Pr and La to reduce hole concentration. The 123 compositions were PrxY1-xBa2Cu3O7 (x = 0.2, 0.3, 0.4) and YLa0.3Ba1.7Cu3O7. The 124 compounds were PrxY1-xBa2Cu4O8 (x = 0.2, 0.3) and YLa0.3Ba1.7Cu4O8. Oxygen isotope experiments in materials with these compositions have shown substantial isotope shifts. The authors found that (a) the Cu isotope shifts are also substantial, but somewhat smaller, (b) the Cu isotope exponent alpha_[Cu] is positive, (c) alpha_[Cu] increases rapidly as Tc is reduced by substitution and rises to a substantial fraction of the BCS value, behavior that is similar to that of the oxygen isotope exponent alpha_O, and (d) when Tc is reduced by non-isovalent substitution, both alpha_O and alpha_[Cu] increase greatly, but the ratio alpha_[Cu]/alpha_O remains 0.75 +- 0.1 in both 123 and 124, regardless of the amount and site of the non-isovalent substitution.

Bi Cuprates

Angle-resolved photoemission data by Z.-X. Shen (Stanford) et al. above and below the superconducting transition temperature Tc of Bi2Sr2CaCu2O8+d (Bi-2212) reveal momentum-dependent changes that extend up to an energy of about 300 meV (or 40 k_BTc). The data suggest an anomalous transfer of spectral weight from one momentum to another, involving a sizable momentum transfer Q ~ (0.45 pi,0). The authors note that the observed Q is intriguingly near the required charge-order periodicity if fluctuating charge stripes are present.

The spectral function of the electron-phonon interaction alpha^2F(omega) determined by a tunneling experiment has been compared by D. Shimada (Shizuoka) et al. with the calculated phonon density of states for Bi2Sr2CaCu2O8+d. The authors find considerable agreement between the two spectra. In particular, they find that a large dip in alpha^2F(omega) at 27 meV is reproduced in the calculated density of states. The authors also present the atomic polarization vectors and the frequencies of the most important modes, and they conclude that vibrations of oxygen atoms along the c axis and low-frequency cation vibrations are especially important.

Cleaved surfaces of Bi2Sr2CaCu2O8+d (Tc = 86 K) have been investigated by S. Kaneko (Tokyo Tech) et al. using low-temperature scanning tunneling spectroscopy. The clean surface was prepared by cleaving the sample at liquid-helium temperature in a vacuum. The tunneling spectra have a broad bump, consisting of two peaks at bias voltages ~30 mV and ~40 mV, just outside a superconducting gap. Because of the broad bump, the spectra cannot be fitted by the theoretical bulk density of states of either s-wave or d-wave superconductors. The authors note that the shape of the measured spectra is similar to the spectra calculated in the 2D Hubbard model.

(Bi,Pb)2Sr2Ca2Cu3O10+d/Ag coils and magnets have been fabricated by N. V. Vo (Los Alamos) using both the wind-and-react (W-R) and the react- and-wind (R-W) approach. The author constructed a test magnet from double pancake coils fabricated by the W-R procedure; the magnet generated a field of ~30 mT at 77 K. Superconducting straps were used to connect the double pancakes.

Superconducting joints between monofilamentary Ag-sheathed Bi2Sr2Ca2Cu3O10+d tapes have been investigated by M. R. Koblischka (Oslo) et al. using magneto-optical imaging. Two types of joints were studied, one with direct contact between the tape cores, and the other with a Ag layer between them. The local flux distributions directly revealed the obstacles hindering the current flow through the joints. The joints with direct contact between tape cores had a critical current about 80% of that of the original tape, while the joints with a Ag layer between them were considerably worse. The difference became even more pronounced in applied magnetic fields.

A related paper by M. R. Koblischka (Oslo) et al. reports magneto- optical imaging of the entry and exit of magnetic flux into a Ag- sheathed Bi2Sr2Ca2Cu3O10+d multifilamentary tape in an applied magnetic field. In low fields, the shielding currents were found to flow mostly in the outermost filaments. The magneto-optical flux patterns also revealed that the filaments in the tape are coupled together, which enables current to flow around defects within the filaments.

As reported by V. Rouessac et al. (Caen), transport critical current measurements have been performed at 77 K on bulk silver-free (Bi,Pb)2Sr2Ca2Cu3O10+d ceramics textured by the sinter-forging method. The authors discuss the influences of the 85 K superconducting 2212 phase and the nonsuperconducting secondary phases, such as (SrxCa1- x)2PbO4, (Sr,Ca)14Cu24Oy, and (SrxCa1-x)2CuO3, in terms of their amounts, grain sizes, shapes, and distribution within the 2223 matrix. The authors also demonstrate the importance of the temperature profile and the atmosphere during post sinter-forging annealing.

A preprint by S. Kambe (Yamagata) et al. reports the effect of pressing and Li doping on the properties of Ag-sheathed Bi-2223 tapes. The authors found that increasing the pressing pressure from 1 t/cm^2 to 10 t/cm^2 increased I_c, and that doping of 0.1-0.3 Li at% increased I_c by about 10%.

Other Cuprates

A mixed solid/vapor phase synthesis route for HgBa2CuO4+d (Hg-1201) using a remote source of mercury has been developed by G. B. Peacock et al. (Birmingham). By this route, the authors were able to obtain a highly underdoped state (Tc <= 35 K) of superconducting HgBa2CuO4+d.

As reported by A. Tampieri (Faenza) et al., Hg1-xMxBa2CuO4+d (where x = 0 or 0.2 with M = V or Pb) compounds have been prepared by hot isostatic pressing (HIP) starting directly with simple oxides canned in a silver tube. The authors report that this is an effective way to prepare large amounts of Hg-1201 superconductor with high purity.

High-resolution x-ray powder diffraction studies of the crystallographic phase transition from the orthorhombic (LTO1) phase to the low- temperature tetragonal (LTT) phase in La1.88-ySr0.12NdyCuO4 (y = 0, 0.1, 0.2, and 0.4) are reported by A. R. Moodenbaugh (Brookhaven) et al. The authors report that the development of the LTT phase is a two-step process.

As reported by Y. Cao et al. (TCSUH), the transition temperature Tc of the high-temperature superconductor YSr2Cu3O7.5 has been measured under hydrostatic pressures up to 1.7 GPa. The Tc was observed to increase from 62.6 K to 67.8 K. The authors note that such a large positive dTc/dP of ~3 K/GPa is unexpected, since thermogravimetric and thermopower measurements indicate that the sample is heavily doped.

Thin Films

A model, based only on universal properties of high-Tc superconductors, to account for the transport characteristics of grain boundaries in these materials is discussed in a preprint by H. Hilgenkamp and J. Mannhart (Augsburg). The model accounts for both the superconducting and normal-state transport properties observed in a comprehensive study of YBa2Cu3O7-d [001]-tilt bicrystalline grain boundaries with varying misorientation angles and of two different symmetries.

Thin-film and bulk [001] tilt, bicrystal grain boundaries in YBa2Cu3O7-d exhibit a strong dependence of the critical current density on misorientation angle. K. E. Gray et al. (Argonne) point out that what is particularly difficult to understand is that Jc is thirty times lower in bulk grain boundaries, which are microscopically more perfect, i.e., minimally faceted and free of impurity phases. The authors propose a plausible explanation based on differences of the pinning of Josephson vortices in the two grain-boundary types. They note that meandering of the grain boundary is desirable for biaxially textured coated-conductor applications to enhance Jc.

A preprint by J.-T. Kim (KRISS) et al. reports measurements of the in- plane longitudinal resistivities of YBa2Cu3O7-d films before and after Sn ion irradiation with matching field B_[phi] = 1 T as a function of magnetic field H (<= 6 T) and temperature T. Near the critical temperature, the fluctuation part of the conductivity sigma*_[xx](T,H) of the unirradiated sample was found to obey 3D XY scaling with dynamic critical exponent z = 1.86 +- 0.1 and static critical exponent nu ~~ 0.669. The irradiated film deviates from 3D XY scaling, especially at low fields.

The angular dependence of the longitudinal and Hall resistivities of YBa2Cu3O7-d films with and without columnar defects has been studied by D. H. Kim (Yeungnam) et al. The Hall conductivity |sigma_[xy]| of an irradiated film shows a sharp increase with decreasing temperature when an external magnetic field is aligned parallel to the columnar defects, while |sigma_[xy]| of an unirradiated film shows a broad minimum in the same orientation. The Hall conductivity thus exhibits a strong pinning dependence.

A preprint by Y. Li and K. Tanabe (SRL-ISTEC) reports a study of the effects of target composition upon the properties of epitaxial NdBa2Cu3O7-d superconducting thin films deposited on SrTiO3 (100), LaAlO3 (100), and NdGaO3 (110) substrates by pulsed laser deposition using slightly Ba-rich Nd1-xBa2+xCu3O7-d (x = 0.00, 0.03, 0.05, and 0.10) targets. The highest zero-resistance transition temperature, 94 K, was obtained for x = 0.03. The critical current density Jc in a 1000 Angstroms thick, 5 micrometers wide bridge was 3.8 x 10^6 A/cm^2 at 77 K in zero field. The authors report target and substrate optimization conditions for obtaining smooth, nearly outgrowth-free film surfaces.

Applications

The effect of a square array of holes (antidots) in the washer of a YBCO bicrystal rf SQUID upon the low-frequency (1/f) noise has been investigated by P. Selders et al. (Juelich). The authors found that the noise was greatly reduced at a set of magnetic fields that geometrically relate the vortex lattice and the antidot lattice well below the fundamental matching field B_m = phi_0/d^2 (d = antidot lattice parameter).

The performance of a five-pole Tchebycheff microstrip low-pass filter (5.3 GHz cutoff frequency) made of a YBCO thin film grown on a LaAlO3 substrate is reported in a paper by M. S. Boutboul et al. (LDIM, Paris). The average insertion loss and the rejection slope were found to be appreciably better with the superconducting filter than with a gold filter made using the same pattern. The performance of the YBCO filter remained approximately constant up to the transition temperature.

The underlying theory for the behavior of a mesoscopic SNS transistor is described in a preprint by F. K. Wilhelm (Karlsruhe) et al. In this device, the quasiparticle distribution can be driven far from equilibrium by a voltage applied across the normal metal. This reduces the supercurrent between the superconducting electrodes, which creates the possibility to use these SNS junctions as fast switches and transistors.

Theory

A theory that depends on competition between intertwin d-wave coupling and a relatively enhanced s-wave component on the surface has been developed by R. Haslinger and R. Joynt (Wisconsin-Madison) to explain the existence of Josephson tunneling between YBa2Cu3O7-d and Pb with the current flowing along the YBCO c axis. The theory appears to explain, at least qualitatively, all observations made to date.

As shown by M. B. Walker and P. Pairor (Toronto), surface bound states in a discrete-lattice model of a dx2-y2 cuprate superconductor are, in general, coherent superpositions of an incoming excitation and more than one outgoing excitation. The authors develop a graphical construction based on a surface Brillouin zone to describe these bound states. In addition, the authors explain the origin of a momentum-dependent lifetime contribution to the width of the bound states as observed in tunneling experiments.

The phase diagram for a 2D metal with variable carrier density has been studied by V. P. Gusynin (Kiev) et al. using the modulus-phase representation for the order parameter. This amounts to splitting the degrees of freedom into neutral fermions and charged boson degrees of freedom. The resulting phase diagram contains a new phase in addition to the superconducting (Berezinskii-Kosterlitz-Thouless) and normal (Fermi-liquid) phases. The authors identify this phase with the pseudogap phase observed in underdoped high-Tc superconductors above their critical temperature.

According to a preprint by E. A. Pashitskii (Kiev) et al., the square- root Van Hove singularity in the density of states nu(E_F) ~ (E_F - E_0)^[-1/2], associated with the extended saddle-point features in the electronic spectra of cuprates with hole-type conductivity, leads to a nonmonotonic dependence of the critical temperature Tc upon the position of the Fermi level E_F with respect to the bottom E_0 of the saddle. As a result of cancellation of the divergence of nu(E_F) in the electron- electron coupling constant, renormalized by strong-coupling effects, the authors show that Tc approaches zero in the limit E_F--> E_0, contrary to the result in the weak-coupling approximation, which gives a finite (and close to maximal) value of Tc for E_F--> E_0. The authors also find that the dependence of Tc on the concentration of doped holes, obtained in the strong-coupling approximation, agrees qualitatively with experimental data for the overdoped cuprates.

A single-particle spectral density is proposed by A. S. Alexandrov (Loughborough) for cuprates, taking into account bipolaron formation, realistic band structure, thermal fluctuations, and disorder. The author explains tunneling and photoemission (PES) spectra, including the temperature-independent gap observed in both the superconducting and normal states, the emission-injection asymmetry, the finite zero-bias conductance, the spectral shape in the gap region and its temperature and doping dependence, and dip-hump incoherent asymmetric features at high voltage (tunneling) and large binding energy (PES).

A microscopic model describing the combined effect of the Hund coupling and the local Coulomb repulsion on the ground-state properties of the layered perovskite compound Sr2RuO4 has been formulated by M. Cuoco et al. (Salerno). Considering that the properties of this compound are determined mainly by the electron dynamics in the RuO2 planes, the authors performed an exact diagonalization on small planar RuO2, RuO4, and Ru2O7 clusters, using the Lanczos algorithm. The authors found that the minimum value of the Hund coupling J needed to have a local triplet spin state on each Ru atom is a rapidly decreasing function of the intra-orbital d-electron Coulomb repulsion U. From an analysis of the off-site spin-spin correlation function, the authors also found that Sr2RuO4 behaves as a paramagnetic metal, in agreement with the experiments.

Overviews

An extensive review of flux pinning in the high-temperature superconductors, focusing on RBa2Cu3O7-d, has been prepared by H. W. Weber (Atominstitut-Wien). The author discusses the mixed-state phase diagram, weak versus strong pinning, experimental techniques, the fishtail effect, flux pinning by various kinds of pinning centers (artificial pinning centers, normal-conducting inclusions, extended planar defects, and radiation-induced defects), critical current densities and irreversibility lines, and field mapping and levitation forces (248 refs.).

A preprint by R. A. Klemm (Argonne) presents an overview of experiments that give evidence concerning the symmetry of the order parameter in the high-temperature superconductors. The author considers three classes of experiments: transport and thermodynamic measurements, angle-resolved photoemission spectroscopy (ARPES), and Josephson tunneling experiments. The author finds that the experiments are not consistent with one another and hence concludes that the symmetry of the order parameter in the high-temperature superconductors is still unknown (49 refs.).

Ph.D. Thesis

The Ph.D. thesis of H. S. Somal (Groningen) reports polarized angle- resolved infrared spectroscopy (PARIS) measurements in the high- temperature superconductors La1.85Sr0.15CuO4 (Tc = 32 K), optimally doped Tl2Ba2CuO6 (Tc = 85 K), overdoped Tl2Ba2CuO6+d (Tc = 30 K), Bi2Sr2CuO6 (Tc = 12 K), and Nd1.85Ce0.15CuO4 (23 K), probing both the ab-plane and c-axis electrodynamics. The predictions of the interlayer tunneling (ILT) model were found not to hold for the Tl, Bi, and Nd cuprates (159 refs.).

Contributed by John R. Clem

Contents: Technology News is on page 6; Preprints begin on page 6; Coming Events begin on page 12; and Resources are 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.

Scientists at the National Research Institute for Metals (Tsukuba, Japan), in collaboration with colleagues at the Showa Electric Wire and Cable Co., Ltd. (SWCC), have developed a novel fabrication procedure for Bi-2212/Ag composite tapes aimed at improving their superconducting properties. The PAIR (Pre-Annealing and Intermediate Rolling) process is the combination of pre-annealing and subsequent intermediate rolling, and is performed prior to melt-solidification. By pre-annealing at 1133 K in oxygen (1 atm) and intermediate rolling with 25% deformation, PAIR- processed samples produced transport Jc(oxide) values (4.2 K, 10 T) exceeding 500,000 A/cm2, which corresponds to Jc(conductor) values of 900 A/mm2. Samples melt-solidified without the PAIR process have Jc(oxide) values of 300,000 A/cm2. The enhancement of Jc is attributed to the microstructure with high grain alignment and uniformity, as well as the improvement in grain connectivity achieved by the PAIR process. For information, contact Kitaguchi Hitoshi, National Research Institute for Metals, 1-2-1, Sengen, Tsukuba 305-0047, Japan; phone +81-298-59- 2329; fax +81-298-59-2301; e-mail cond-mat@xxx.lanl.gov (#9803127). 74.20.-z.

M. I. Alonso, M. Garriga, S. Pinol, and M. Brinkmann, "Doping Dependence of the Ellipsometric Spectra of Nd2-xCexCuO4-d Single Crystals." To be published in Physica C (in press). Institut de Ciencia de Materials de Barcelona, CSIC, Campus de la UAB, E-08193 Bellaterra, SPAIN; telephone +34 3 580 1853; telefax +34 3 580 5729; e-mail mat@xxx.lanl.gov (#9803274). Key words: reentrance, peak effect curve, effect of disorder, 2H-NbSe2. 74.60.-w; 74.25.Dw; 64.70.Dv.

M. T. Beal-Mond, "Discussion of Various Hybrid Pairings for Orthorhombic YBCO Compounds and Possible Experiments." To be published in Physica C (in press). Laboratoire de Physique des Solides, Universite Paris-Sud, Batiment 510, F-91405 Orsay Cedex, FRANCE. Key words: orthorhombic YBCO compounds, hybrid pairings, models.

M. S. Boutboul, H. Kokabi, and M. Pyee, "Microwave Microstrip Low-Pass Filters Using High-Tc Superconducting YBaCuO Thin Films on LaAIO3." To be published in Physica C (in press). Contact H. Kokabi, Laboratoire LDIM, Tour 12, 2 eme etage, Universite Pierre et Marie Curie 4, Place Jussieu, F-75252 Paris Cedex 05, FRANCE; telephone +33 1 4427 4371; telefax +33 1 4427 4382; e-mail kokabi@moka.ccr.jussieu.fr. Key words: YBaCuO thin film, magnetron sputtering, Tchebychev microstrip.

Ernst Helmut Brandt, "Geometric Barrier and Current String in Type-II Superconductors Obtained from Continuum Electrodynamics." Submitted to Phys. Rev. Lett. Max Planck Institut fuer Metallforschung, P.O.B. 800665, D-70506 Stuttgart, GERMANY; telephone +49 711 689 1823; telefax +49 711 689 1010; e-mail ehb@physix.mpi-stuttgart.mpg.de. 74.60.Ge; 74.60.Ec.

Ernst Helmut Brandt, "Magnetic Response of Superconductors in Various Geometries." 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. Max Planck Institut fuer Metallforschung, P.O.B. 800665, D-70506 Stuttgart, GERMANY; telephone +49 711 689 1823; telefax +49 711 689 1010; e-mail ehb@physix.mpi-stuttgart.mpg.de. 74.60.-w; 74.60.Ge.

Cristina Buzea and Tsutomu Yamashita, "Elliptic Function Formalism Description of Anisotropic Ginzburg-Landau Equation." To be published in Physica C (in press). Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980- 77, JAPAN. Key words: Ginzburg-Landau equation, superconducting parameters. 74.20.De.

Y. Cao, T. L. Hudson, Y. S. Wang, S. H. Xu, Y. Y. Xue, and C. W. Chu, "Study of the High Temperature Superconductor YSr2Cu3O7.5 Under Pressure." Preprint #98:029; submitted to Phys. Rev. B. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail mat@xxx.lanl.gov (#9803390). 74.60.Ge; 05.20.-y.

Mark W. Coffey, "Fundamental Inversion Problem for the Magnetic Force Microscopy of Superconductors." To be published in Phys. Rev. B. Department of Chemistry, University of Colorado, Denver, CO 80217; telephone (303) 499-2114; telefax (303) 497-5316; e-mail mcoffey@newton.colorado.edu. 74.20.De; 02.30.-f; 74.25.Nf; 74.25.Ha.

Mark W. Coffey, "On the Inertial Mass of a Vortex in High-Tc Superconductors: Closed Form Results." To be published in J. Phys. A. Department of Chemistry, University of Colorado, Denver, CO 80217; telephone (303) 499-2114; telefax (303) 497-5316; e-mail mcoffey@newton.colorado.edu. Key words: Bogoliubov-de Gennes equations, inertial mass, vortex mobility, core dielectric constant, core polarizability, type-II superconductivity, vortex dynamics. 74.20.Mn; 74.20.De; 74.60.Ge; 74.72.-h.

Mark W. Coffey, "Magnetic Force Microscopy of Superconductors." Presented at the Chandrasekhar Memorial Symp., Oct. 1996; to be published in Int. J. Eng. Sci. Department of Chemistry, University of Colorado, Denver, CO 80217; telephone (303) 499-2114; telefax (303) 497- 5316; e-mail mcoffey@newton.colorado.edu. Key words: forward problem, inverse problem, magnetic force microscopy, Meissner state, mixed state, kernel function, penetration depth, London theory, Hankel transformation, Laplace transformation, Schroedinger equation, Ricatti equation.

Mark W. Coffey, "Modeling the Electrodynamic Response of Composite Superconducting Structures in the Mixed State." To be presented at the Fourth Int. Conf. on Math. and Numer. Aspects of Wave Propagation, June 1998. Department of Chemistry, University of Colorado, Denver, CO 80217; telephone (303) 499-2114; telefax (303) 497-5316; e-mail mcoffey@newton.colorado.edu.

A. Conde-Gallardo, T. Klein, C. Escribe-Filippini, J. Marcus, T. Lopez- Rios, and M. Jergel, "Tl2Ba2CaCu2O8-x Superconducting Films Deposited by Aerosol and Their Hysteretic ac Losses." To be published in Physica C (in press). Contact T. Klein, Laboratoire d'Etudes des Proprietes Electroniques des Solides, Centre National de la Recherche Scientifique, BP166, F-38042 Grenoble Cedex 9, FRANCE; telefax +33 4 76 88 7688; e- mail klein@lepes.polycnrs-gre.fr. Key words: Tl-2212 films, ac susceptibility, flux pinning, ac losses. 74.60.Ge.

Mario Cuoco, Canio Noce, and Alfonso Romano, "Interplay Between Hund Coupling and Hubbard Interaction in Sr2RuO4." To be published in Phys. Rev. B. Contact Canio Noce, Dipartimento di Scienze Fisiche "E. R. Caianiello," Universita degli Studi di Salerno, Via S. Allende, I-84081 Baronissi, (Salerno), ITALY; e-mail canio@vaxsa.csied.unisa.it.

M. Daeumling, "ac Power Loss for Superconducting Strips of Arbitrary Thickness in the Critical State Carrying a Transport Current." To be published in Supercond. Sci. & Technol. Department of Electric Power Engineering, Bldg. 325, Technical University of Denmark, DK-2800 Lyngby, DENMARK; e-mail m.daumling@nkt-rc.dk. 74.60.-w.

J. P. Emerson, D. A. Wright, B. F. Woodfield, J. E. Gordon, R. A. Fisher, and N. E. Phillips, "Specific Heat of YBa2Cu3O7-d, 0 <= d <= 0.2: Spin-2 and Spin-1/2 Paramagnetic Centers." Department of Chemistry, University of California and Lawrence Berkeley Laboratory, Berkeley, CA 94720. 74.25.Bt; 74.25.Ha; 74.72.Bk.

M. Faiz, M. Ahmed, N. M. Hamdan, Kh. A. Ziq, and J. Shirokoff, "Study of Metal Distributions in YBa2Cu3O7-x/Ag2O Composites." To be published in Supercond. Sci. & Technol. Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261, SAUDI ARABIA; e-mail sac-phys@dpc.kfupm.edu.sa.

D. Giller, Y. Abulafia, R. Prozorov, Y. Wolfus, A. Shaulov, and Y. Yeshurun, "Local Voltage-Current Characteristics in High-Tc Superconductors." To be published in Phys. Rev. B. Institute of Superconductivity, Department of Physics, Bar Ilan University, Ramat Gan 52900, ISRAEL; Y. Yeshurun's telephone +972 3 53-18433 or -18434; telefax +972 3 53-53298. 74.60.-w; 74.72.-h; 74.25.Ha; 74.60.Ge.

K. E. Gray, M. B. Field, and D. J. Miller, "Explanation of Low Critical Currents in Flat, Bulk vs. Meandering, Thin-Film [001] Tilt Bicrystal Grain Boundaries in YBa2Cu3O7." 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.

D. P. Grindatto, J.-C. Grivel, G. Grasso, H.-U. Nissen, and R. Fluekiger, "TEM Study of the (Bi,Pb)2Sr2Ca2Cu3Ox Phase Formation in (Bi,Pb)2Sr2Ca2Cu3Ox Silver-Sheathed Tapes." To be published in Physica C (in press). Laboratorium fuer Festkoerperphysik, ETH Zurich, CH-8093 Zurich, SWITZERLAND. Key words: (Bi,Pb)2Sr2Ca2Cu3Ox, transmission electron microscopy (TEM), phase formation, superconducting tape.

Valery P. Gusynin, Vadim M. Loktev, Rachel M. Quick, and Sergei G. Sharapov, "Pseudogap Phase Formation in the Crossover from Bose-Einstein Condensation to BCS Superconductivity in Low Dimensional Systems." Presented at the First Int. Conf. on New Theories, Discoveries, and Applications of Superconductors and Related Materials (New3SC-1), Baton Rouge, La., Feb. 19-24, 1998; to be published in Int. J. Mod. Phys. B. Contact Sergei G. Sharapov, Department of Physics, University of Pretoria, 0002 Pretoria, SOUTH AFRICA; e-mail sharapov@scientia.up.ac.za; preprint also available at cond- mat@xxx.lanl.gov (#9803142).

G. C. Han, C. K. Ong, and H. P. Li, "ac Susceptibility of (Bi,Pb)2Sr2Ca2Cu3Oy/Ag Tape in Perpendicular ac Fields." To be published in Physica C (in press). Department of Physics, National University of Singapore, Singapore 119260, SINGAPORE. Key words: susceptibility, BiSrCaCuO, scaling, critical state model. 74.60.Ge; 74.60.Jg.

*Hideki Haneda, Takehiko Ishiguro, Satoshi Watauchi, Jun-ichi Shimoyama, and Kohji Kishio, "Intrinsic Pinning of the Josephson Vortex in a Two- Dimensional Superconductor Bi2Sr2CaCu2O8+d Studied via the Conversion of Ultrasonic to Electromagnetic Waves." To be published in J. Phys. Soc. Jpn. Department of Physics, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-01, JAPAN; e-mail haneda@ss.scphys.kyoto-u.ac.jp. Key words: intrinsic pinning, Josephson vortex, two-dimensional superconductor, mutual conversion between electromagnetic waves and ultrasonic waves. *Revised version.

Robert Haslinger and Robert Joynt, "Theory of Josephson Tunneling Along the c-Axis of YBCO." Department of Physics and Applied Superconductivity Center, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706-1390; e-mail haslinger@landau.physics.wisc.edu; preprint also available at cond- mat@xxx.lanl.gov (#9803124). 95.30.Cq; 97.10.Cv; 97.60.Jd.

J.-K. Heinsohn, D. Reimer, A. Richter, K.-O. Subke, and M. Schilling, "Interaction of Process Parameters in the Laser Deposition of YBa2Cu3O7 Films." To be published in Physica C (in press). Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, D-20355 Hamburg, GERMANY. Key words: laser deposition, YBa2Cu3O7 film, KrF excimer laser.

H. Hilgenkamp and J. Mannhart, "Superconducting and Normal-State Properties of YBa2Cu3O7-d-Bicrystal Grain Boundary Junctions in Thin Films." Submitted to Appl. Phys. Lett. Experimentalphysik VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, Universitaetsstr. 1, D-86135 Augsburg, GERMANY; telephone +49 821 598 3653; telefax +49 821 598 3652; e-mail hans.hilgenkamp@physik.uni-augsburg.de.

K. Kajantie, M. Karjalainen, M. Laine, J. Peisa, and A. Rajantie, "Thermodynamics of Gauge-Invariant U(1) Vortices from Lattice Monte Carlo Simulations." Theory Division, CERN, CH-1211 Geneve 23, SWITZERLAND; e-mail keijo.kajantie@cern.ch; preprint also available at hep-ph@xxx.lanl.gov (#9803367). 98.80.Cq; 11.27.+d; 11.15.Ha; 67.40.Vs; 74.60.-w.

S. Kambe, Y. C. Guo, S. X. Dou, H. K. Liu, Y. Wakahara, H. Maeda, K. Kakimoto, and M. Yavuz, "Effect of Pressing and Li-Doping on Superconducting Properties of Ag-Sheathed Bi-2223 Tapes." To be published in Supercond. Sci. & Technol. Contact M. Yavuz, Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-77, JAPAN; telephone +81 22 215 2705; telefax +81 22 215 2071; e- mail myavuz@imr.tohoku.ac.jp.

Shin-ichi Kaneko, Nobuhiko Nishida, Kohshi Mochiku, and Kazuo Kadowaki, "Scanning Tunneling Spectroscopy of Bi2Sr2CaCu2O8+d." To be published in Physica C (in press). Department of Physics, Tokyo Institute of Technology, Tokyo 152, JAPAN. Key words: scanning tunneling spectroscopy, scanning tunneling microscopy, Bi2Sr2CaCu2O8-d, energy gap. 74.50.+r; 61.16.Ch; 74.72.Hs.

D. H. Kim, J. H. Park, Y. H. Kim, J. M. Lee, T. S. Hahn, J. D. Hettinger, and K. E. Gray, "Angular Dependence of the Hall Conductivity in YBa2Cu3Ox Films with Columnar Defects." Submitted to Phys. Rev. B. Department of Physics, Yeungnam University, Kyungsan 712-749, KOREA; preprint also available from Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e- mail janice_coble@qmgate.anl.gov. 74.25.Fy.

Jin-Tae Kim, W. N. Kang, H. R. Lim, D. H. Kim, Y. K. Park, J.-C. Park, C. H. Kim, T. S. Hahn, S. S. Choi, J. D. Hettinger, and K. E. Gray, "Pinning Effect on Critical Dynamics in YBa2Cu3O7-d Films with Weak Disorder and with Columnar Defects." To be published in Physica C. Superconductivity Group, Korea Research Institute of Standards and Science, P.O. Box 102, Yusong, Taejon, 305-600, KOREA; preprint also available from Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov. 74.60.Ge; 74.60.Ec; 74.40.+k.

J. R. Kirtley, K. A. Moler, G. Villard, and A. Maignan, "c-Axis Penetration Depth of Hg-1201 Single Crystals." Submitted to Phys. Rev. Lett. IBM Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598-0218; e-mail kirtley@watson.ibm.com; preprint also available at cond-mat@xxx.lanl.gov (#9803312).

Richard A. Klemm, "What is the Symmetry of the High Tc Order Parameter?" Presented at the First Int. Conf. on New Theories, Discoveries, and Applications of Superconductors and Related Materials (New3SC-1), Baton Rouge, La., Feb. 19-24, 1998; to be published in Int. J. Mod. Phys. 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.

M. R. Koblischka, T. H. Johansen, H. Bratsberg, and P. Vase, "Flux Distributions in Jointed Bi2Sr2Ca2Cu3O10+d Tapes." To be published in Supercond. Sci. & Technol. Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 1-16-25 Shibaura, Minato-ku, Tokyo 105, JAPAN; telefax +81 3 3454 9287; e-mail koblischka@istec.or.jp; T. H. Johansen's e-mail at University of Oslo in Norway is t.h.johansen@fys.uio.no. 74.60.Ec; 74.60.Ge; 74.60.Jg.

M. R. Koblischka, T. H. Johansen, H. Bratsberg, and P. Vase, "Study of Flux Entry and Exit into Bi-2223 Multifilamentary Tapes." To be published in Supercond. Sci. & Technol. Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 1-16-25 Shibaura, Minato-ku, Tokyo 105, JAPAN; telefax +81 3 3454 9287; e-mail koblischka@istec.or.jp; T. H. Johansen's e-mail at University of Oslo in Norway is t.h.johansen@fys.uio.no.

N. Kristoffel and T. OErd, "On the Fluctuation-Induced Superconductivity Pseudogap." To be published in Physica C (in press). Institute of Physics, University of Tartu, Riia 142, EE2400 Tartu, ESTONIA; telefax +372 7 383033; e-mail kolja@fi.tartu.ee. Key words: superconductivity, pseudogap, fluctuation. 74.20.-z.

W. K. Kwok, L. M. Paulius, V. M. Vinokur, A. M. Petrean, R. M. Ronningen, and G. W. Crabtree, "Anisotropically Splayed and Columnar Defects in Untwinned YBa2Cu3O7-d." Submitted to Phys. Rev. B. Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov. 74.60.Ge.

Yijie Li and K. Tanabe, "Effect of Target Composition on Properties of NdBa2Cu3O7-d Superconducting Thin Films Grown by Pulsed Laser Deposition: A Comparative Study." Submitted to J. Appl. Phys. Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone +81 3 3536 5709; telefax +81 3 3536 5717; e-mail yjli@istec.or.jp.

A. P. Litvinchuk, "Comment on 'Temperature Dependence of the Raman- Active B_[1g] and A_[1g] Modes in YNi2B2C.'" Preprint #98:028; submitted to Phys. Rev. B. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu. 63.20.Kr; 74.20.Fg; 78.30.-j.

J. Loos and J. A. Morkowski, "Polaron-Type Transformations of the t-t'-J Model." To be published in Physica C (in press). Contact J. A. Morkowski, Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, POLAND; telephone +48 61 8612 320; telefax +48 61 8684 524; e-mail jmorkows@ifmpan.poznan.pl. Key words: spin-charge separation, magnons, spin polaron. 71.27.+a; 72.10.Di; 74.20.Mn.

T. Matsushita, A. Shimogawa, and M. Asano, "Observation of Structure of Electric Field on the Surface of Superconducting Pb-In Slab Under a Longitudinal Magnetic Field." To be published in Physica C (in press). Department of Computer Science and Electronics, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka 820, JAPAN; telefax +81 948 29 7683; e- mail matusita@cse.kyutech.ac.jp. Key words: superconducting Pb-In slab, current-voltage characteristics, longitudinal magnetic field.

H. Miao, H. Kitaguchi, H. Kumakura, and K. Togano, "Microstructure and Superconducting Properties of Pb-Substituted Bi2Sr2CaCu2Ox/Ag Dip-Coated Tapes." To be published in Physica C (in press). Contact H. Kitaguchi, National Research Institute for Metals, 1-2-1 Sengen, Tsukuba 305, JAPAN; telefax +81 298 59 2301; e-mail hk@nrim.go.jphk@nrim.go.jp Key words: Pb- substitution, Bi-2212/Ag, textured microstructure, transport Jc, grain boundary. 74.72.Hs; 85.25.Kx.

A. R. Moodenbaugh, Lijun Wu, Yimei Zhu, L. H. Lewis, and D. E. Cox, "High Resolution X-ray Diffraction Study of La1.88-ySr0.12NdyCuO4." Submitted to Phys. Rev. B. Department of Applied Science, Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11973-5000; telephone (516) 344-3870; telefax (516) 344-4071; e-mail moodenba@bnl.gov. 74.72.Dn; 74.62.Dh; 61.10.Nz.

D. E. Morris, A.P.B. Sinha, V. Kirtikar, and A. V. Inyushkin, "Copper Isotope Shifts in Pr and La Substituted 123 and 124 Cuprate Superconductors; Comparison with Oxygen Isotope Shifts." To be published in Physica C (in press). Contact A.P.B. Sinha, Morris Research, Inc., 44 Marguerita Road, Berkeley, CA 96707; telephone (510) 525-3070; telefax (510) 548-5485.

V. A. Murashov, J. Horvat, M. Ionescu, A. A. Bush, H. K. Liu, and S. X. Dou, "Dependence of Critical Current Density and Irreversibility Field on the Oxygen Disordering for Single Domain Melt-Textured Y-123." To be published in Physica C (in press). Contact J. Horvat, Center for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, AUSTRALIA; telephone +61 42 21 4731; telefax +61 42 21 5731; e-mail jhorvat@uow.edu.au. Key words: Y- 123 melt texture, flux pinning, critical current, oxygen content, irreversibility field.

T. Nagashima, K. Takemae, K. Sumiyoshi, J. Wakabayashi, T. Mochiku, and K. Kadowaki, "Relaxation of Local Magnetization of Single-Crystalline Bi2Sr2CaCu2O8 at Low Temperatures." To be published in Physica C (in press). Department of Physics, Chuo University, Bunkyo-ku, Tokyo 112, JAPAN. Key words: magnetic field, temperature dependence, relaxation rate.

S. K. Nikogosyan, A. A. Sahakyan, H. N. Yeritsyan, V. A. Grigoryan, E. G. Zargaryan, and A. G. Sarkissyan, "Superconducting Properties of YBa2Cu3-xFexOy Ceramics with Small x." To be published in Physica C (in press). Yerevan Physics Institute, Radiation Physics Laboratory, 2 Alikhanian Brothers Street, Yerevan 375036, ARMENIA. Key words: high- temperature superconductors (HTSs), ac susceptibility, transition temperature, pinning centers.

Henrik Nordborg and Gianni Blatter, "Numerical Study of Vortex Matter Using the Bose Model: First-Order Melting and Entanglement." Preprint #ETH-TH/98-06; submitted to Phys. Rev. Lett. Institut fuer Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich, SWITZERLAND; preprint also available from Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov; or at cond-mat@xxx.lanl.gov (#9803041). 74.20.De; 74.60.Ec; 05.30.Jp.

Naoki Ohashi, Takashi Ohyama, Mirnoru Takemoto, Takaaki Tsurumi, Junzo Tanaka, and Osamu Fukunaga, "Variation of La 3d Photoelectron Spectra of La1.9Sr1.1-xCaxCu2O6+d." To be published in Physica C (in press). Department of Inorganic Materials, Faculty of Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152, JAPAN; telephone +81 3 5734 2829; telefax +81 3 5734 2514; e-mail nohashi@ceram.titech.ac.jp. Key words: core-level region, interatomic distance, cation-substituted system, photoelectron spectra, relative intensity ratio.

Kichambare Padmakar, Kijima Norihito, Honma Hiroshi, Ebisu Shuji, and Nagata Shoichi, "Probing Giant Reduction of Tc in the Li(Ti1-xVx)2O4 Spinel System." To be published in Appl. Supercond. (in press). Department of Chemistry, Indian Institute of Technology, Powai, Mumbai 400 076, INDIA.

E. A. Pashitskii, V. I. Pentegov, and E. Abraham, "About the Influence of Square-Root Van Hove Singularity on the Critical Temperature of High- Tc Superconductors." To be published in JETP Lett. Contact V. I. Pentegov, Institute of Physics, National Academy of Sciences of Ukraine, 46 Nauki Avenue, Kiev 252650, UKRAINE; e-mail pentegov@iop.kiev.ua; preprint also available at cond-mat@xxx.lanl.gov (#9803081). 74.20.-z; 74.25.Dw; 74.62.-c; 74.62.Dh.

G. B. Peacock, A. Fletcher, I. Gameson, and P. P. Edwards, "Synthesis and Superconductivity of Highly Underdoped HgBa2CuO4+d." Submitted to Physica C. School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UNITED KINGDOM; e-mail g.b.peacock@bham.ac.uk. Key words: mercurocuprates, synthesis, underdoping, aerial oxidation.

J. P. Rodriguez, "Critical Behavior of Layered Superconducting Films in Parallel Magnetic Field." Instituto de Ciencia de Materiales, Consejo Superior de Investigaciones Cientificas, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid, SPAIN; preprint also available at cond- mat@xxx.lanl.gov (#9710116). 74.20.De; 74.20.Mn; 74.60.Ge; 74.80.Dm.

V. Rouessac, G. Poullain, J. Provost, M. Gomina, and G. Desgardin, "Influence of the Secondary Phases and Post-Annealing on the Transport Current Density of Sinter-Forged (Bi,Pb)-2223 Ceramics." Presented at Materiaux Supraconducteurs a haute Tc, Caen, France, March 26-27, 1997; to be published in Eur. Phys. J. Appl. Phys. Laboratoire CRISMAT-ISMRA, Universite de Caen, CNRS UMR 6508, 6 Bd. Marechal Juin, F-14050 Caen Cedex, FRANCE; e-mail ceram@crismat.ismra.fr. 74.60.Jg; 74.72.Hs; 81.40.Rs.

Manas Sardar, "Phonon Softening in Bilayer Cuprate Superconductors Due to Interlayer Pair Tunneling." To be published in Physica C (in press). Material Science Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603102, INDIA; telephone +91 4114 40396; e-mail msd@igcar.ernet.in.

P. Selders, A. Castellanos, M. Vaupel, and R. Woerdenweber, "Observation of and Noise Reduction by Vortex Lattice Matching in YBa2Cu3O7 Thin Films and rf SQUIDs with Regular Arrays of Antidots." To be published in Appl. Supercond. Institute fuer Schicht und Ionentechnik, Forschungszentrum Juelich, D-52425 Juelich, GERMANY.

Z.-X. Shen, P. J. White, D. L. Feng, C. Kim, G. D. Gu, H. Ikeda, R. Yoshizaki, and N. Koshizuka, "Temperature Induced Momentum Dependent Spectral Weight Transfer in Bi2Sr2CaCu2O8+d." To be published in Science. Department of Applied Physics, Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, CA 94305.

D. Shimada, N. Tsuda, U. Paltzer, and F. W. de Wette, "Tunneling Phonon Structures and the Calculated Phonon Density of States for Bi2Sr2CaCu2O8." To be published in Physica C (in press). Department of Physics, Shizuoka University, 836 Ohya, Shizuoka 422, JAPAN; telephone +81 45 238 4742; telefax +81 45 238 0993; e-mail qyr00634@niftyserve.or.jp. Key words: electron-phonon interaction, tunneling, phonon dispersion relations, Bi2Sr2CaCu2O8. 74.50.+r; 74.25.Kc; 74.72.Hs; 63.20.Dj.

H. S. Somal, "Polarized Angle Resolved Infrared Spectroscopy of High Temperature Superconductors." Submitted as a Ph.D. thesis (University of Groningen). Contact D. van der Marel, Solid State Physics Laboratory, University of Groningen, Nijenborgh 4, 9747 AG Groningen, THE NETHERLANDS; telephone +31 50 363-7229 or -4826; telefax +31 50 363- 4825; e-mail marel@phys.rug.nl.

Minoru Tagami, M. Nakamura, Yoshihiro Sugawara, Yuichi Ikuhara, and Yuh Shiohara, "Interface Structures of Heteroepitaxially Grown Pr123/Y123 and Pr123/Nd123 Crystals by Liquid Phase Epitaxy." To be published in Physica C (in press). Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone +81 3 3536-5703 through -5705; telefax +81 3 3536-5714 or -5717. Key words: epitaxial growth, interface structure, YBa2Cu3O7-d, PrBa2Cu3O7-d, NdBa2Cu3O7-d, misfit dislocation.

A. Tampieri, G. Calestani, G. Celotti, C. Micheletti, and D. Rinaldi, "Preparation of Hg-1201 Superconductor by Hot Isostatic Pressing." To be published in Physica C (in press). IRTEC-CNR, via Granarolo 64, I- 48018 Faenza, ITALY. Key words: Hg-1201, hot-isostatic-pressing (HIP), superconductivity.

W. H. Tang and J. Gao, "Influence of Nd at Ba Sites on Superconductivity of YBa2-xNdxCu3Oy." To be published in Physica C (in press). Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong, PEOPLE'S REPUBLIC OF CHINA. Key words: x-ray powder diffraction, YBa2-xNdxCu3Oy, Ba site. 74.62.Dh; 74.62.Bf; 74.72.Bk.

Tetsuo Tsuchiya, Kazuo Fueki, and Tadashi Koyama, "Chemical Thermodynamics of Hg1201 and Hg1223 Phases." To be published in Physica C (in press). Department of Industrial Chemistry, Faculty of Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda-shi, Chiba 278, JAPAN. Key words: Hg1201 superconductor, Hg1223 superconductor, oxygen non-stoichiometry, thermodynamical stability, Hg, Cu valence states.

N.V.N. Viswanath and T. Rajasekharan, "Refinement of Insulating Sm2BaCuO5 Phase and its Effect on Jc in Melt Processed SmBa2Cu3Oy System." To be published in Physica C (in press). Defence Metallurgical Research Laboratory, P.O. Kanchanbagh, Hyderabad 500 058, INDIA. Key words: microstructure, precipitate, melt processing.

N. V. Vo, "Fabrication of Wind-React and React-Wind High Temperature Superconducting Bi-2223/Ag Coils and Magnets." Preprint #LA-UR-98-1294; to be published in J. Magn. & Magn. Mater. Superconductivity Technology Center, Los Alamos National Laboratory, Mail Stop G755, Los Alamos, NM 87545; telephone (505) 665-6859; telefax (505) 665-3164; e-mail nvv@lanl.govnvv@lanl.gov.

M. B. Walker and P. Pairor, "Discrete-Lattice Model for Surface Bound States and Tunneling in d-Wave Superconductors." Department of Physics, University of Toronto, Toronto, Ontario, CANADA M5S 1A7; e-mail walker@physics.utoronto.ca; preprint also available at cond- mat@xxx.lanl.gov (#9803079). 74.20.-z; 74.25.Jb; 74.50.+r; 74.80.Fp.

Harald W. Weber, "Flux Pinning." To be published in the Handbook on the Physics and Chemistry of Rare Earths, Special Volumes on High Temperature Rare Earth Superconductors, edited by K. A. Gschneidner, Jr., L. Eyring, and M. B. Maple. Atomic Institute of the Austrian Universities, Schuettelstrasse 115, A-1020 Vienna, AUSTRIA.

W. Wei, J. Schwartz, K. C. Goretta, U. Balachandran, and A. Bhargava, "Effects of Nanosize MgO Additions to Bulk Bi2.1Sr1.7CaCu2Ox." To be published in Physica C (in press). National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310. Key words: Bi-2212, nanosize MgO, flux pinning.

Frank K. Wilhelm, Gerd Schoen, and Andrei D. Zaikin, "The Mesoscopic SNS Transistor." Submitted to Phys. Rev. Lett. Institut fuer Theoretische Festkoerperphysik, Universitaet Karlsruhe, Engesserstr. 7, Physikhochhaus, D-76128 Karlsruhe, GERMANY; telephone +49 721 608 3370; telefax +49 721 69 8150; e-mail wilhelm@tfp.physik.uni-karlsruhe.de; preprint also available at cond-mat@xxx.lanl.gov (#9803091).

Winnie Wong-Ng, Lawrence P. Cook, and William Greenwood, "Melting of Sr14Cu24O41 at Oxygen Pressures of 0.0075, 0.021 and 0.1 MPa." To be published in Physica C (in press). Ceramics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899. Key words: Sr14Cu24O41 melting, oxygen pressure, 0.0075 MPa, 0.021 MPa; 0.1 MPa.

D. A. Wright, J. P. Emerson, B. F. Woodfield, J. E. Gordon, R. A. Fisher, and N. E. Phillips, "Low-Temperature Specific Heat of YBa2Cu3O7- d, 0 <= d <= 0.2: Evidence for d-Wave Pairing." Department of Chemistry, University of California and Lawrence Berkeley National Laboratory, Berkeley, CA 94720. 74.25.Bt; 74.72.Bk.

X. M. Xiong, Y. L. Zhou, H. B. Lu, Z. H. Chen, and G. Z. Yang, "Preparation of Y-Ba-Cu-O Films on Polycrystalline Metal Substrates with Biaxially Aligned Yttria-Stabilized Zirconia Buffer Layers Deposited by Ion Beam Assisted Pulsed Laser Deposition." To be published in Physica C (in press). Laboratory of Optical Physics, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, PEOPLE'S REPUBLIC OF CHINA; e-mail xmxiong@aphy02.iphy.ac.cn. Key words: thin film, metallic substrate, buffer layers, ion-beam bombardment, YSZ.

T. Yamashita, J. A. Alarco, J. Riches, A. Bhargava, J. C. Barry, and I.D.R. Mackinnon, "Binder Effect on Microstructure and Properties of YBa2Cu3O7-x Extruded Wires." To be published in Physica C (in press). Advanced Ceramics Development, UniQuest, University of Queensland, St. Lucia, Queensland 4072, AUSTRALIA. Key words: long lengths of wires, YBa2Cu3O7-x, HPMC.

T. Yasuda and I. Iguchi, "Observation of Anomalously Long Relaxation Phenomena in Pb3BiSx Thin Films Under Pulsed Magnetic Field." To be published in Physica C (in press). LSI Division, Kawasaki Steel Corporation, 166 Haga-dai, Haga-machi, Haga-gun, Tochigi 321-33, JAPAN. Key words: Pb3BiSx thin films, pulsed magnetic field, relaxation time.

Y. Yu, Z. Y. Zeng, X. N. Xu, H. M. Shao, M. J. Qin, X. Jin, X. X. Yao, X. S. Rong, B. Ying, and Z. X. Zhao, "Temperature Dependence of the Critical Current Determined from Magnetic Relaxation in HgBa2Ca2Cu3O8+d." To be published in Physica C (in press). Department of Physics and Laboratory of Microstructure of Solid States, Nanjing University, P.O. Box 2020, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA; e-mail scmb@netra.nju.edu.cn. 74.60.Ge; 74.60.Jg.

Th. Zahner, R. Stierstorfer, R. Roessler, J. D. Pedarnig, D. Baeuerle, and H. Lengfellner, "Anisotropic Resistivity in Off-c-Axis Grown Bi2Sr2CaCu2O8 Films." To be published in Physica C (in press). Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, D-93040 Regensburg, GERMANY; telefax +49 941 943 4223; e- mail thomas.zahner@physik.uni-regensburg.de. Key words: Bi2Sr2CaCu2O8, off-axis growth, anisotropic resistivity.

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

July 20 - 24, 1998: School on Mesoscopic Electronics, International Centre of Condensed Matter Physics, Universidade De Brasilia, Brazil. Topics are: introduction to mesoscopic physics, Coulomb blockade, review of disordered mesoscopic physics experiments, chaotic transport in microstructures, thermodynamics of disordered mesoscopic systems, experiments in ballistic microstructures, nonlinear effects in mesoscopic transport, correlation effects in quantum dots, transfer matrix and DMPK equation, M-I transition and interaction effects. For further information, contact School on Mesoscopic Electronics, International Centre of Condensed Matter Physics, CP 04513 Campus Universitario Darcy Ribeiro, CEP 70919-970, Brazil-DF; e-mail meso@iccmp.br; Web site http://www.if.uerj.br/~caio/meso.html.

*Sept. 6 - 11, 1998: Gordon Research Conference on Superconductivity: Cuprate Superconductors and Related Materials, Queen's College, Oxford, United Kingdom. Colin Gough and Bertram Batlogg, Co-Chairs; M. Brian Maple, Vice-Chair. Sessions are: recent theoretical developments, influence of pairing symmetry on properties, normal-state pseudogap, c- axis conduction, new materials, proximity coupling with CMR and other materials. For information, contact Gordon Research Conferences, University of Rhode Island, P.O. Box 984, West Kingston, RI 02892-0984; telephone (401) 783-4011; telefax (401) 783-7644; e-mail app@grcmail.grc.uri.edu (for application form requests) or grc@grcmail.grc.uri.edu (for general information).

Sept. 14 - 25, 1998: NATO Advanced Study Institute -- Material Science, Fundamental Properties and Future Electronic Applications of High-Tc Superconductors, Albena, Bulgaria. Purpose is to help young physicists in their initial research in the field of HTS and related topics, and to support creation of the atmosphere of collaboration between physicists from NATO and Cooperative Partner countries. Aimed at scientists at the postdoctoral level with an appropriate scientific background. Subjects include: electronic structure of novel superconductors and related materials, Fermi surface mapping by angle-resolved photoemission, d-wave superconductivity, application of Eliashberg theory, and anomalous normal-state properties of HTS. Special attention will be paid to classical problems in the physics of superconductivity: Ginzburg-Landau and London theories and their application to theory of plasma waves in superconducting systems, surface phase transitions, hydro-dynamic relations for superconductors, dynamics and pinning of vortices in HTS, electrodynamics, magnetic susceptibility, optical properties, tunneling, fluctuation phenomena in super-conductors. Will also include phenomenology of supercon-ductivity: practical applications, superconducting field effect transistors, electric field effects in superconductors, and grain boundary and other material effects. Application deadline, May 30, 1998. For information, contact T. Mishonov, Department of Theoretical Physics, Faculty of Physics, University of Sofia, 5, J. Bourchier Blvd., 1164 Sofia, Bulgaria; telephone +359 2 256 652; telefax +359 2 96 252 76; e-mail mishonov@rose.phys.uni-sofia.bg.

Nov. 16 - 19, 1998: 11th International Symposium on Superconductivity (ISS'98), Fukuoka Sunpalace Hotel, Fukuoka, Japan. Organized by the International Superconductivity Technology Center (ISTEC). Symposium will consist of oral and poster sessions and invited talks in the following topics: Physics -- theory, physical properties, and new measurement techniques; Chemistry -- new materials and syntheses, substitution, solid-state chemistry, and properties; Critical Current -- flux-pinning mechanism, vortex physics, and weak links; Wires, Tapes, and Bulk -- solid-state powder ceramics, chemical-solution processing, melting solidification, and chemical-vapor deposition; Films and Junctions -- processing, properties, lithography, junction fabrication, and physics; Device Applications -- digital, analog, SQUID, and other electronic devices; System Applications -- power, power transportation, magnets, magnetic shields, and other system applications; Standardization -- standardization for electromagnetic, mechanical, and microwave properties measurements. Will also include exhibition of materials and devices. Abstract deadline, June 30, 1998; exhibit application deadline, July 31, 1998. Proceedings to be published. Official language is English. For further information, contact ISS'98 Secretariat, ISTEC, Eishin Kaihatsu Bldg. 6F, 34-3 Shimbashi 5-chome, Minato-ku, Tokyo 105-0004, Japan; telephone +81 3 3431-4002; telefax +81 3 3431-4044.

RESOURCES

Information

Proceedings: High-Temperature Superconductivity: Ten Years After Its Discovery, proceedings of the International Workshop on High-Temperature Superconductivity, Jaipur, India (Dec. 16-21, 1996), edited by K. B. Garg and S. M. Bose. This volume reviews the progress in the high-Tc superconductivity field in the last ten years, and discusses future directions and the differences in viewpoints that need to be resolved. Issues discussed range from theories to microscopic and macroscopic applications. Publ. 1998; 437 pp.; price $25; ISBN 81-7319-155-7. For information, contact K. B. Garg, Condensed Matter Physics Laboratory, Department of Physics, University of Rajasthan, Jaipur - 302 004, India; telephone +91 141-519767; telefax +91 141-511912; e-mail krishna@jp1.vsnl.net.in. Or contact S. M. Bose, College of Arts and Sciences, Drexel University, Philadelphia, PA 19104; telephone (215) 895-2620 or -2718; telefax (215) 895-4999; e-mail bose@duvm.ocs.drexel.edu.

Proceedings: M-Calc II -- Proceedings of the Military and Commercial Applications of Low-Cost Cryocoolers (Jan. 15-16, 1998). Sponsored by the Electronic Industries Association (EIA) in cooperation from DARPA, NRL, and NVESD. For information, contact EIA ALCEM, Department 287, Washington, DC 20055; telephone (703) 907-7546; telefax (703) 907-7549; e-mail cryo@eia.org.

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, #8, April 15, 1998.