HIGH-Tc UPDATE E-MAIL VERSION, VOL. 12, NO. 17, Sept. 1, 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, and other agencies, organizations, and individuals.

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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:

YBCO Coated Conductors

The fabrication of YBa2Cu3O7-d coated conductors with a layer sequence of YBCO/YSZ/CeO2/Ni is reported by M. Paranthaman et al. (Oak Ridge). Cube (100) texture in the starting Ni substrates was obtained by cold rolling followed by recrystallization. A thin CeO2 layer of thickness 100-200 Angstroms was then grown using an e-beam evaporation technique, followed by a thick YSZ (yttria-stabilized zirconia) layer, grown by either e-beam evaporation, which resulted in a porous film, or rf magnetron sputtering, which resulted in a dense film. YBCO films (~0.8 micrometer), grown by pulsed laser deposition, had zero-field transport critical current densities of ~1 x 10^6 A/cm^2 at 77 K on both e-beam and sputtered YSZ layers. A related paper by M. Paranthaman et al. (Oak Ridge) describes results of studies using buffer layers of RAlO3 (R = La, Nd, Gd, and Y) and NdGaO3 grown epitaxially on SrTiO3 (100) using sol-gel precursors.

The properties of buffer-layer candidates for YBCO coated-conductor technology, BaCeO3 and Ce0.75Zr0.25O2, prepared from sol-gel precursors, are reported by G. N. Glavee (Oak Ridge and Lawrence University) et al.

RBa2Cu3O7-d

The 123 compound (La1-xCax)(Ba1.75-xLa0.25+x)Cu2Oy (x = 0.1 and 0.4) has been used by O. Chmaissem (Argonne) et al. to study both the superconducting transition temperature Tc and the degree of buckling of the CuO2 plane as a function of oxygen doping over the entire doping range from underdoped to overdoped. The authors have found that both Tc and the buckling go through a maximum at the same oxygen composition, suggesting a common origin for the behavior of Tc and the buckling. Previous work on the 123 compound and other high-Tc superconductors has led to the conclusion that CuO2-plane buckling lowers Tc for a fixed chemical composition. Thus, the authors conclude that the observation of a maximum in the buckling at the maximum Tc shows that, as the composition is changed to increase Tc, there is a structural response that competes with superconductivity.

A preprint by D. N. Basov (UC-San Diego) et al. reports on a study of the optical conductivity of single crystals of the high-Tc superconductor YBa2Cu4O8 in which superconductivity is suppressed by random substitution of Cu with Zn. The a-axis infrared spectrum, which is a direct measure of the charge dynamics in the CuO2 planes, is dominated by a bound state at 120 cm^[-1]. The data reveal a connection between quasiparticle localization and suppression of the superfluid density that is qualitatively different from the conventional dirty- limit scenario. The authors thus suggest that localization may be in part responsible for the degradation of Tc in disordered underdoped cuprates, while in the optimally and overdoped materials the suppression of superconductivity occurs primarily because of anisotropy of the order parameter.

Measurements of the magnetization and levitation force of various superconducting rings made of melt-textured YBa2Cu3O7-d have been carried out by H. Zheng (Argonne) et al. These measurements were then compared with those after a slit was cut into the rings, preventing shielding currents from forming closed loops around the perimeter. For most of the rings studied, the ratio of the magnetization without and with a slit was equal to the theoretical value derived from the Bean model. However, some of the rings showed ratios much below this value; magneto-optical imaging revealed that these rings contained defective areas (weak links) where magnetic flux can readily enter, thereby preventing the establishment of large-diameter circulating shielding currents.

Nonlinear microwave emission by YBa2Cu3O7-d single crystals at temperatures close to Tc has been investigated by A. Agliolo Gallitto and M. Li Vigni (Palermo). The authors studied the second- and third- harmonic signals as a function of the temperature, input power, and external magnetic field. The authors propose a phenomenological theory, which accounts for some of the observed behavior.

XANES measurements at the Pr L_[III] edge have been performed by E. Alleno (LCMTR-CNRS, Thiais) et al. to determine the valence v of Pr in several compounds. In Y0.8Pr0.2Ba2Cu3O6.95, v = 3.4+-0.1; in PrBa2Cu3O6.94, v = 3.18+-0.05; and in PrBa2Cu3-xCoxOy, v decreases progressively upon Co doping to v = 3.0 for x ~ 0.4-0.5, where it remains constant for x > 0.5.

The effects of oxygen partial pressure P_[O2] on the solubility limits of the light rare earth R (R = Pr, Nd, Sm, Eu, and Gd) in solid solutions of R1+xBa2-xCu3O7-d have been determined by H. Wu et al. (Ames Lab, Iowa State). The authors stress that an understanding of P_[O2] and the temperature dependence of the solubility limits will not only provide guidelines for obtaining high Tc in R1+xBa2-xCu3O7-d but also clarify the flux-pinning mechanism in these systems.

The relationship between the oxygen content and the superconducting properties of a series of Nd1+xBa2-xCu3O7-d (0 <= x <= 0.4) solid solutions has been studied by N. Chikumoto et al. (SRL-ISTEC).

Single crystals of Y1-xNdxBa2Cu3O7-d solid solutions (0.098 <= x <= 0.410) have been grown by X. Yao et al. (SRL-ISTEC) using the crystal pulling method. A critical temperature of 89+-2 K was obtained from oxygenated Y1-xNdxBa2Cu3O7-d single crystals held at 340^oC for 200 h, but Tc could be enhanced up to 91 K by annealing at 500^oC for three days.

Bi Cuprates

Angle-resolved photoemission spectroscopy (ARPES) has been carried out by I. Vobornik (EPFL) et al. and R. Gatt (Wisconsin) et al. on overdoped samples of Bi2Sr2CaCu2O8+d (Bi-2212). The authors found that nodes of the superconducting energy gap, which are present for optimally doped samples, are not observed for overdoped Bi2Sr2CaCu2O8+d. This is a surprising result, because the normal-state electronic band structure for optimally doped and overdoped samples is similar. The authors of both papers conclude that the observations are inconsistent with a pure d_[x^2-y^2] order-parameter symmetry. Gatt et al. argue that the change from zero gap at optimal doping to a nonzero gap for overdoping arises from a superconducting order parameter that is intrinsically two- component, with the relative weights varying with doping.

A preprint by S. Misra (Wisconsin) et al. reports an analysis of photoemission data for several doping levels of the Bi2Sr2CaCu2O8+d compounds, ranging from overdoped to underdoped. The authors find that the high-frequency part of the spectra near (0,pi) can be described by Fermi-liquid theory in the overdoped regime, but exhibits a non-Fermi- liquid behavior in the underdoped regime. The authors also show that this behavior fits reasonably well to a 1/sqrt[omega] behavior, which has been suggested for systems with strong spin fluctuations.

The point-contact tunneling technique has been used by L. Ozyuzer (Argonne, Illinois Institute of Technology, and Izmir Institute of Technology) et al. to examine quasiparticle and Josephson currents in overdoped Bi2Sr2CaCu2O8+d (Bi-2212) single crystals with bulk Tc values near 62 K. Superconductor-insulator-normal metal (SIN) tunnel junctions were formed between the Bi-2212 crystals and a Au tip, which displayed well-resolved quasiparticle gap features including sharp conductance peaks. SIS junctions also were obtained between two pieces of the Bi- 2212 crystals, resulting in simultaneous quasiparticle and Josephson currents. The authors found that the dynamic conductances of both SIN and SIS junctions were qualitatively similar to those found on optimally doped Bi-2212 but with reduced gap values (Delta = 15-20 meV).

The nonlinear, c-axis interlayer electrical properties of Bi2Sr2CaCu2O8+d (Bi-2212) single crystals in the normal and superconducting states have been investigated by I.F.G. Parker (Birmingham) et al. Measurements of the I-V characteristics and dynamic conductivity across lithographically defined stacks of intrinsic junctions on the surface of single crystals of various doping are reported. The authors find that the increase in c-axis resistance at low temperatures is related to the emergence of a normal-state pseudogap. The authors conclude that either (a) the magnitude of the pseudogap in the normal state and the gap in the superconducting state in bulk Bi-2212 crystals are almost an order of magnitude smaller than those deduced from surface ARPES and vacuum tunneling measurements or (b) if the gaps are indeed as large as deduced from the latter measurements, the c-axis quasiparticle conduction in both the normal and superconducting states must involve coherent tunneling across the intrinsic junctions formed between the CuO2 bilayers.

As reported by Y. N. Tsay (Brookhaven) et al., bulk Bi2Sr2CaCu2O8+d (Bi- 2212) bicrystals containing a single high-quality [001] twist grain- boundary junction were prepared to investigate the orbital symmetry of the superconducting order parameter in highly anisotropic Bi-based high- temperature superconductors. The misorientation angles of the bicrystals ranged from 0 degree to 180 degrees. The microstructure in the vicinity of the junction was characterized using high-resolution, nanoprobe analytical microscopy. The authors found that some high-angle twist junctions were able to carry a critical current density similar to their constituent single crystals. The authors conclude that the results cannot be interpreted in terms of a pure d_[x^2-y^2]-wave order parameter.

Electronic Raman scattering has been studied by O. V. Misochko (ISSP- Chernogolovka) and G. Gu (New South Wales) in single-crystal Bi2Sr2Ca(Cu1-xFex)2O8+d for different Fe concentrations. Two observed features in the data are consistent with unconventional pairing. However, the crossover scale to a cubic dependence in the B_[1g] channel decreases with increasing Fe concentration, contrary to d-pairing expectations.

Studies of the fishtail effect in the magnetization hysteresis (M-H) loops of Bi2Sr2CaCu2O8+d (Bi-2212) crystals grown by the spiral or layer-by-layer growth mechanism are reported by X. L. Wang et al. (Wollongong). The authors found that a strong fishtail effect with H_[peak] = 1000-2000 Oe between 20 and 50 K occurred for both high-Tc (86 K) and low-Tc (76 K, oxygen underdoping) spiral-grown samples, and that this feature disappeared when the spirals were removed from the crystal surface. A weak fishtail effect with H_[peak] = 300 Oe between 20 and 40 K was observed for layer-by-layer-grown crystals with smooth surfaces, but the peak was found to be reversible by annealing in oxygen or nitrogen.

Vortices

Relations between the vortex-core charge and vortex bound states have been investigated by N. Hayashi et al. (Okayama) using the Bogoliubov-de Gennes theory. The authors calculated both the structure of the carrier density around a static single vortex and its temperature dependence. The authors also point out a relation between the charging of the vortex core and the Caroli-de Gennes-Matricon vortex bound states, which may permit the extraction of information about the vortex core charge from scanning tunneling microscopy (STM) measurements.

The quantized energy spectrum and quasiparticle eigenfunctions for low- lying excitations in the mixed state of clean d-wave superconductors have been calculated by A. S. Mel'nikov (Nizhny Novgorod). The author's study is based on an approximate analytical solution of the Bogoliubov- de Gennes equations for both rectangular and triangular vortex lattices with one of the primitive translations chosen parallel to the gap-node direction.

As shown by J. Shiraishi (Tokyo) et al., a rhombic vortex lattice (i.e., a square lattice tilted by 45 degrees away from the a axis) is stable in a wide field region in d-wave superconductors in a magnetic field parallel to the c axis. The triangular lattice in a weak magnetic field transforms into the rhombic vortex lattice at a magnetic field of order kappa^[-1]H_[c2](T) with a second-order transition, where kappa is the Ginzburg-Landau parameter. The transition is the standard second-order transition as described by Landau, and a corresponding jump in the specific heat is expected: Delta[C] ~ T(del[H_[cr]/del[T])^2.

The distribution of thermally excited vortex loops near a superfluid phase transition has been calculated by G. A. Williams (UCLA) using a renormalized theory. The author stresses that the results should apply to not only high-Tc superconductors but also liquid helium and cosmic strings in the early universe.

The latent heat of vortex-lattice melting has been measured by A. Schilling (Zurich) et al. for varying angles theta between the external magnetic field H and the c-axis of an untwinned YBa2Cu3O7-d single crystal. The authors find that the discontinuity in entropy at melting, Delta[S] per unit volume of sample, depends solely on the temperature T where melting occurs, and does not depend on theta and the corresponding melting field H_m(T,theta). The T dependence of Delta[S] near the critical temperature Tc can be quantitatively explained by a recently developed theory based on the London model accounting for the strong T dependence of the model parameters near Tc.

A preprint by L. Bulaevskii (Los Alamos) et al. derives a relation connecting the Josephson plasma resonance frequency omega_p(B,T) to the density correlation function of the 2D pancake vortex liquid. The relation allows the extraction of quantitative information about the c- axis correlations of pancake vortices in crystals with weak and strong pinning from experimental observations of the magnetic-field dependence of the plasma resonance.

The boson Hubbard model has been used by R. A. Lehrer and D. R. Nelson (Harvard) to model vortex lines in superconductors with a magnetic field parallel to a periodic array of columnar pins. The model uses the analogy between vortex lines and the statistical mechanics of quantum bosons. When the magnetic field has a component perpendicular to the pins, the analogy yields a novel non-Hermitian boson Hubbard model.

Magnetization measurements on untwinned YBa2Cu3O7-d have been performed by T. Nishizaki (Tohoku) et al. in magnetic fields up to 27 T using Hall-probe magnetometry. The authors studied the anomalous second peak in the magnetization near the multicritical point. Below the second peak, the vortex pinning force shows a steep increase at a characteristic field H*(T), which is connected with both the first-order vortex-lattice melting line T_m(H) and the second-order vortex-glass transition line T_g(H) at the multicritical point. The authors discuss the origin of H*(T) in terms of a field-driven transition from the ordered Bragg glass to the disordered vortex-glass phase.

A theory of interactions between vortices in superconductors and local magnetic moments has been developed by I. F. Lyuksyutov (Texas A&M) and V. Pokrovsky (Texas A&M and Landau Institute). The authors apply their results to superconducting films with magnetic nanoscale dots and experiments on rare-earth nickel borocarbide magnetic superconductors.

A preprint by J. R. Kirtley (IBM-Yorktown) et al. presents a solution to the anisotropic London equation for an interlayer Josephson vortex parallel to the planes as the vortex approaches the surface and the associated magnetic field spreads into the space outside the superconductor. The calculations are in good agreement with available experiments on vortices in Tl2Ba2CuO6+d (Tl-2201), allowing a quantitative determination of the interlayer penetration depth lambda_c.

The ground states and ordering behavior on cooling in the liquid regime of Josephson vortices of a layered superconductor in fields parallel to the layers have been considered theoretically by R. Ikeda and K. Isotani (Kyoto) using the lowest-Landau-level approximation for the Lawrence- Doniach model. In a narrow field range below the stability region of the pinned rhombic solid with no vacant interlayer spacings, the authors find that a waving structure seen in a recent numerical simulation becomes the true ground state, and that a thermal fluctuation correction to the mean-field energy is necessary to stabilize other pinned hexagonal solids realizable in lower fields.

The pinning force on vortices parallel to the layers in superconductor - normal-metal - superconductor (SNS) multilayers has been calculated by S. L. Prischepa (Minsk) et al. as a function of temperature, magnetic field, and normal-layer thickness using the Ginzburg-Landau theory. The results are in good agreement with recent experiments on Nb/Pd multilayers.

Commensurability effects between the superconducting vortex lattice and a square lattice of submicron holes (period 1 micrometer and diameter 0.4 micrometer) in 1500 Angstroms vanadium films have been studied by V. Metlushko (Argonne) et al. using atomic force microscopy (AFM), dc magnetization, ac susceptibility, magnetoresistivity, and I-V measurements. Peaks in the magnetization and critical current at matching fields were found to depend nonlinearly upon the value of the external ac field or current, as well as the inferred symmetry of the vortex lattice.

Critical State

Nonlinear two-dimensional transport current flow J(r) in superconductors with power-law voltage-current characteristics E proportional to J^n (n >> 1) has been studied by A. Gurevich and J. McDonald (Wisconsin). The authors used a general method based on a hodograph transformation, which reduces this nonlinear problem to the solution of a linear London equation with an inverse screening length beta = (n-1)/2sqrt[n] for a plate with cuts. The authors obtained analytic solutions for nonlinear current flow around a planar defect, which causes anisotropic long-range disturbances of J(r) on the scale asqrt[n] much larger than the defect width 2a, and large stagnation regions of magnetic flux near the defect.

A generalized critical-state approach for type-II superconductors, based on a variational principle, has been developed by A. Badia et al. (Zaragoza). The free energy is minimized subject to the constraint |J(r)| <= Jc for the macroscopic current density, which poses the problem in the framework of optimal control theory. The authors use this method to deal with multicomponent field situations, such as that of a current-carrying superconductor subjected to an external applied field.

Thin Films

Measurements of the critical current density Jc in epitaxial YBa2Cu3O7-d thin films have been carried out by X. W. Cao (Hefei) et al. as a function of applied magnetic field, temperature, and angle between the magnetic field and the ab plane. The authors find a sharp change in the behavior of Jc above and below the vortex-glass transition line.

An extensive study of the electric and thermomagnetic properties of an underdoped, an optimally doped, and an overdoped c-axis-oriented epitaxial Nd2-xCexCuO4 thin film has been investigated by F. Gollnik (Tuebingen) and M. Naito (NTT) in the temperature range 4.2-300 K and in magnetic fields up to 11 T perpendicular to the CuO2 planes. Numerous transport properties of the normal and superconducting state are reported.

The microstructures at the interfaces of YBa2Cu3O7-d and PrBa2Cu3O7-d thin films grown homoepitaxially on (001), (100), and (110) oriented YBa2Cu3O7-d single crystals by rf sputtering and metalorganic chemical vapor deposition (MOCVD) have been studied by J. G. Wen et al. (SRL- ISTEC) using transmission electron microscopy. The authors found that the surface state before deposition strongly influenced the microstructure of the film.

Thermal annealing effects on the microstructure of the grain boundaries of 36.8 degrees and 24 degrees symmetric [100] tilt SrTiO3 bicrystals have been studied by Q. D. Jiang (TCSUH) et al. Annealing the substrates at temperatures as low as 780^oC led to the formation of grooves at the grain boundaries, providing direct evidence that the thickness depression of YBa2Cu3O7-d films deposited over bicrystal boundaries originates from the underlying grooved substrates. The authors propose a simple structure model to explain the 1/theta dependence of the normalized critical currents flowing across the grain boundary.

Multilayers

The dependence of the critical temperature on n in (BaCuO2)2/(CaCuO2)n (n = 1-6) superlattices has been investigated by G. Balestrino (Roma) et al. The authors found that Tc reaches its maximum value (about 80 K) for n = 2 and 3 and then decreases for n larger than 3. The authors explain the results by taking into account both the variation of the effective carrier concentration per CuO2 plane and the high degree of structural disorder typical of these artificial structures.

Investigations of the properties of mesa devices of stacked intrinsic junctions using (Bi,Pb)2Sr2Ca2Cu3O10+d thin films are reported by K. Setsune et al. (Matsushita Electric). The authors found that the estimated superconducting gap value increased as the number of intrinsic junctions in the stack was reduced. The I-V curve for the thinnest stack showed the characteristics of a single junction and was well explained assuming d_[x^2-y^2] symmetry for the superconducting order parameter.

The properties of multilayers of interleaving superconducting and nonsuperconducting 123 films are described in a preprint by J. L. Vicent et al. (Madrid). The authors analyzed their results in terms of the anisotropy revealed in measurements of the critical current, resistivity, and upper critical field as a function of the angle of the applied field relative to the c-axis.

The growth and characterization of YBa2Cu3O7-d/PrBa2Cu3O7-d multilayers are reported in a preprint by B. R. Zhao (Beijing) et al.

The interplay of superconductivity and magnetism in proximity-coupled systems has been studied by Y. Bruynseraede et al. (Leuven), who measured the critical temperature Tc, upper critical field H_[c2], and critical current I_c of [Nb(400 Angstroms)/Fe(t_[Fe])]5 superlattices. The authors found that the Fe layers are ferromagnetic only for t_[Fe] > 15 Angstroms but that the superconducting Nb layers are already decoupled for t_[Fe] = 12 Angstroms.

Further studies of multilayers are reported for YBCO/PBCO by W. K. Park et al. (Seoul National); BaCuO2/(Ca,Sr)CuO2 by G. Balestrino (Roma) et al.; Nb/CuMn by L. Maritato (Salerno) et al. and L. V. Mercaldo (Maryland and Salerno); and NbN/AlN by Z. H. Barber (Cambridge) et al.

The theory and application of Josephson-coupled multilayers as switching devices in superconducting electronics are addressed in a preprint by S. Lomatch (Northwestern). The author discusses both low-Tc engineered multilayers (e.g., Nb/Al-AlOx and Nb/Al-AlNx stacked systems) and intrinsic high-Tc compounds (e.g., Bi-2212).

Applications

A preprint by J. Rieger et al. (Siemens) reports the development of a 10 m long high-temperature superconducting cable conductor stranded with an industrial winding process from 2 km of Ag/Bi-2223 tapes. The critical current of the conductor was 5 kA. This model of a power transmission cable demonstrated very low ac losses of 0.8 W/m at 2000 A_[rms] at 50 Hz measured with both electric transport and calorimetric methods. The ac losses were found to vary linearly with frequency P proportional to f and to have a current dependence slightly lower than P proportional to I^3. The magnitude of the losses was found to be a factor of three lower than that predicted by the monoblock version of the Bean model. The model for uniform current distribution (UCD) improves the quantitative description of the losses. The authors conclude that their low-loss design of the conductor has potential for use as an economical HTS power transmission cable.

A 15.1 T cryocooled Nb3Sn superconducting magnet with a 52 mm room- temperature bore has been demonstrated by K. Watanabe (Tohoku and CREST) et al. The authors report that the current leads in this system are no longer the dominant heat loads because of the use of high-temperature superconductors. Bi2Sr2Ca2Cu3O10+d current leads with a 23 mm outer diameter, 20 mm inner diameter, and 180 mm length, which carry the critical current of greater than 1000 A at 77 K in the absence of a magnetic field, are connected between Cu current leads and the current terminals of the coils, which are typically at 4-6 K.

The development of a coplanar resonator serving as a tank circuit for rf washer SQUIDs is reported by Y. Zhang et al. (Juelich). The superconducting structures were patterned from 200 nm epitaxial YBCO on 1 mm-thick LaAlO3 substrates.

As reported by P. Silvestrini (Napoli) et al., energy-level quantization in Nb-AlOx-Nb Josephson junctions has been revealed in measurements of the escape rate out of the zero-voltage state as a function of current. The current was swept at rates up to 25 A/s.

The development of a hybrid superconductor-semiconductor memory system to achieve low power (135 mW) and high speed (128 Gb/s) data access between a 16 GHz 8-bit superconducting rapid single flux quantum (RSFQ) vector processor and a 512-kbit complimentary metal-oxide silicon (CMOS) memory system is described in a preprint by Z. J. Deng (UC-Berkeley) et al. The authors present simulations and test results for some circuit components.

Theory

A theoretical description of the superconducting state of under- to overdoped cuprates, based on the short coherence length of these materials and the associated strong pairing fluctuations, has been developed by Q. Chen et al. (Chicago). The dependencies of the calculated Tc and the zero-temperature gap parameter Delta(0) upon the hole concentration x are in semi-quantitative agreement with experiment. Although the ratio 2Delta(0)/k_BTc has a strong x dependence, different from the universal BCS value, and Delta(T) deviates significantly from the BCS prediction, the authors obtain quasi-universal behavior for the normalized superfluid density rho_s(T)/rho_s(0) and the Josephson critical current I_c(T)/I_c(0) as a function of T/Tc. While experiments on rho_s(T) are consistent with these results, future measurements on I_c(T) are needed to test this prediction.

The thermal behavior of superconductors with complex order parameter symmetry has been studied by H. Ghosh (Rio de Janeiro) using a weak- coupling theory. The author uses the theory to explain recent experiments in high-temperature superconductors by K. Krishana et al. [Science 277, 83 (1997)] on magnetothermal conductivity and by J. Ma et al. [Science 267, 862 (1995)] on temperature-dependent gap anisotropy.

The magnetic catalysis of dynamical symmetry breaking has been examined by W. V. Liu (Texas-Austin). The author's model shows that a magnetic field can induce a phase transition associated with parity breaking. The author's calculation is intended to give an explanation of the phase transition observed in a recent experiment by K. Krishana et al. [Science 277, 83 (1997)].

As shown by Y. Bang (Chonnam National), the Migdal theorem is violated in the high-Tc cuprates, and a vertex correction should be included in the gap equation to be consistent with the anomalously strong inelastic scattering in the hot spots, observed in various normal-state experiments. The author finds a strong enhancement of Tc from the vertex correction despite a strong pair-breaking effect due to inelastic scattering.

A model of the electronic spectrum of a two-dimensional system with hot patches on the Fermi surface has been proposed by A. I. Posazhennikova and M. V. Sadovskii (Ekaterinburg). The model leads to an essential renormalization of the spectral density and a pseudogap. The authors use this model to derive the Ginzburg-Landau expansion for both s-wave and d-wave Cooper pairing and analyze the influence of pseudogap formation on the basic properties of superconductors.

The energy spectrum, photoemission pseudogap, and magnetic properties (including a magnetic pseudogap) have been calculated by A. Sherman (Tartu) and M. Schreiber (Chemnitz) using a unified approach based on the 2D t-J model, which has been widely used for the description of CuO2 planes in the high-Tc superconductors. To include properties of the paramagnetic state, the authors extended spin-wave theory with the constraint of zero staggered magnetization. The spectrum was determined by solving numerically a set of self-energy equations for hole and magnon Green's functions in the self-consistent Born approximation for finite hole concentrations x and temperatures T. Theoretically calculated electronic and magnetic properties were found to be in qualitative and in some cases quantitative agreement with experiment.

A preprint by M. Letz (Mainz) and R. J. Gooding (Queen's) reports an investigation of the attractive Hubbard model in the low-density limit for the 2D square lattice. The authors find a quasiparticle lifetime that varies linearly with temperature, similar to many experiments, and although the system has a Fermi surface, it shows non-Fermi-liquid behavior over a wide temperature range.

The I-V characteristics of a 1D Josephson-junction array with charging effect has been numerically investigated by T. Koyama (Tohoku) et al. The hysteresis loops in the I-V curves show a multiple-branch structure, similar to that observed for c-axis transport in single-crystals of high-Tc cuprates.

Starting from a microscopic model for the Josephson effect in a stack of superconducting layers coupled by tunneling barriers, Ch. Preis (Regensburg) et al. have derived a set of equations for the gauge- invariant phase difference in different barriers. The authors used a simplified model to study the nonlinear dynamics of the coupled system.

A preprint by J. Halbritter (Karlsruhe) stresses that tunnel channels via states in the blocking layers have important consequences for charge dynamics in the high-Tc superconductors.

According to A. V. Balatsky and R. Movshovich (Los Alamos), a d_[x^2- y^2]-wave superconductor is marginally stable in the presence of external perturbations. Subjected to external perturbations by magnetic impurities, it develops a secondary component of the gap, complex d_[xy], to maximize the coupling to impurities and lower the total energy. This secondary d_[xy] component exists at high temperatures and produces the full gap ~20 K in the single-particle spectrum around each impurity, apart from impurity-induced broadening. At low temperatures, a phase-ordering transition into a global d_[x^2-y^2] + id_[xy] state occurs.

The c-axis Josephson critical current for bicrystals of high-temperature superconductors with [001] twist grain-boundary junctions has been studied by R. A. Klemm (Argonne) et al. The authors find that measurements of the critical current as a function of the twist angle and temperature should be a useful test of order-parameter symmetry, as it can distinguish between pure s-wave, pure d_[x^2-y^2]-wave, and dominant d_[x^2-y^2]-wave combined with a subdominant s-wave or d_[xy]- wave order parameter.

A nonequilibrium state of a superconductor caused by an external source such as x-rays or gamma-rays and the relaxation of this state have been studied by Yu. V. Ovchinnikov and V. Z. Kresin (LBL, UC-Berkeley). The appearance of quasiparticles in the nonequilibrium state leads to an additional contribution to the tunneling current. The authors evaluate the time dependence of this current in superconducting tunneling detectors.

Other Activities

As discussed by K. Maki and E. Puchkaryov (USC), Sr2RuO4 is most likely a p-wave superconductor. The authors show theoretically that a small amount of impurity scattering not only strongly reduces the superconducting transition temperature but also dramatically modifies the electronic properties. The authors note that their theory agrees well with a recent specific heat measurement in Sr2RuO4.

A preprint by H. Won (Hallym) and K. Maki (USC) briefly discusses the properties of unconventional superconductors and then analyzes the peak in the out-of-plane magnetoresistance in the organic superconductor kappa-(ET)2Cu(NCS)2 in terms of superconducting fluctuation theory. The data suggest that this material is a d-wave superconductor.

Measurements of the in-plane magnetoresistivity rho_[ab](T,H) around the average superconducting transition are presented by J. Mosqueira (Universidad de Santiago de Compostela) et al. The authors studied inhomogeneous YBa2Cu3O7-d (Y-123) and Bi2Sr2CaCu2O8+d (Bi-2212) crystals with small Tc inhomogeneities, associated with small oxygen-content inhomogeneities, nonuniformly distributed throughout the sample volume. The authors were able to explain the measurements using two-dimensional electrical resistor network models.

Overviews

A book chapter by M. Paranthaman and B. C. Chakoumakos (Oak Ridge) reviews the synthesis and characterization of the Ln (Ln = lanthanide and Y) borocarbides. In the LnNi2B2C structure, BNi layers alternate with LnC layers, while in LnNiBC, BNi layers alternate with double LnC layers (83 refs.).

A brief review of the author's theory of a combined mechanism for high- temperature superconductivity mediated by both phonons and local charged bosons (which the author calls lochons) has been prepared by K. P. Sinha (Bangalore). The author stresses that this mechanism can explain high critical temperatures and that it gives the right variation of Tc and the oxygen isotope exponent as a function of doping (45 refs.).

The synthesis and characterization of bulk HgBa2Can-1CunO12n+2+d (n = 1, 2, 3, and 4) are reviewed in a book chapter by M. Paranthaman and B. C. Chakoumakos (Oak Ridge). The authors describe the synthesis of these materials by solid-state reaction from metal oxide components using a single-step process, and they discuss structural details determined by x-ray and neutron powder diffraction data (44 refs.).

A brief overview of some open questions about high-temperature superconductivity has been prepared by C. W. Chu (TCSUH). The author stresses that, in addition to the average charge-carrier concentration in the active-block CuO2 layers, important roles are also played by the doping site, the number of CuO2 layers per unit cell, and details of the charge reservoir. The author also notes that while the anomalous behavior in the underdoped region is rich in physics, its relation to high-temperature superconductivity remains unclear. In addition, the implications of phase separation (charge stripes) also remain to be explored in further detail (15 refs.).

Contributed by John R. Clem

Contents: Technology News begins on page 7; Preprints begin on page 8; Coming Events are on page 15; and FYI is on page 15.

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

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.

Development of long-length high-temperature superconductor tape has been reported by MM Cables in Australia, a division of Metal Manufactures Limited. MM Cables now has the capability of manufacturing Bi-2223 HTS tape in one-thousand-meter continuous lengths and is one of five companies in the world to have demonstrated this capability. The company has exported both tapes and small devices manufactured from the tape to customers in the Asia-Pacific Region. Successful production is the culmination of an extensive research and development effort by a collaborative team involving MM Cables, the University of Wollongong, and the CSIRO Division of Telecommunications and Industrial Physics. The tapes, consisting of 37 filaments of Ag-clad Bi-2223, were manufactured and tested at the MM Cables HTS Development Facility at the Australian Technology Park (Sydney) and processed using the powder-in- tube (PIT) technique. Measurement of the critical current at 77 K with a 1 microvolt/cm criterion, taking into account the effect of the self field, revealed Jc values up to 8000 A/cm^2. MM Cables is also developing a range of alternative and novel HTS wire and tape designs for specific applications. The standard product range includes pure and alloy silver-sheathed tape containing up to 61 filaments and Jc at 77 K up to 20,000 A/cm^2. All tape products can be supplied with a continuous insulating coating. The tapes have been used in the construction of a range of small devices, including an HTS magnet with a 50 mm diameter bore that generated 0.5 T at 4.2 K in a background field of 5 T. The range of filament configurations available include twisted filaments for reduced ac loss, wire-in-tube, tape-in-tube, and stacked filaments for high I_c tapes and current leads. Round wires, which exhibit I_c performance that is independent of the orientation of applied magnetic field, have also been developed. Patent protection has been sought for the outcomes of this development work. For more information, please contact Miles Apperley, MM Cables HTS Development Facility, telephone +61 2 92094221; telefax +61 2 92094222; e-mail milesa@ozemail.com.au.

Successful operation of a space-based experiment testing the performance of HTSC was reported recently, by Asher Space Institute at Technion. The experiment was mounted on the Techsat satellite, which was launched into a low earth orbit on July 10, 1998. Techsat is a miniature satellite built by the Asher Space Institute at Technion-Israel Institute of Technology and designed around the concept of providing a small inexpensive platform for testing new technologies. The satellite weighs 48 kg and its total power budget is 25 W. Housekeeping tasks by the control systems require 10 W, leaving 15 W for all the experiments on board. The HTSC experimental set-up, built at Technion Physics Department, consisted of a thin YBCO film on an MgO substrate patterned into a microbridge. The film is mounted on a miniature cryocooler manufactured by RICOR Inc. (Kibbutz Ein Harod, Israel). A dedicated electronics package measures the R-T curve during cool down and critical current vs. temperature below Tc. The experiment weighs about 500 gm and consumes less than 13 W. It was turned on at specified time intervals for a preset amount of time, in order to test the variations of the superconducting properties with time. A test of the longevity and robustness of HTSC in space is an important input needed to move the satellite communication applications forward. First results indicate that the thin film survived a year's storage, the space qualifying tests, and the launch, with only minor degradation of its properties. For information, contact Emil Polturak, Department of Physics, Technion, Haifa 32000, Israel; telephone +972 4829 2761; telefax +972 4822 1514; e-mail emilp@physics.technion.ac.il. Detailed description of Techsat can be found at the Web site http://techsat.internet-zahav.net.

Contributed by Sreeparna Mitra

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.

E. Alleno, C. Godart, B. Fisher, J. Genossar, L. Patlagan, and G. M. Reisner, "Valence of Pr in Y0.8Pr0.2Ba2Cu3O7 and PrBa2Cu3-xCoxO7 (0 <= x <= 1)." Presented at the Int. Conf. on Strongly Correlated Electron Systems, Paris, France, July 15-18, 1998; to be published in Physica B. Laboratoire de Chimie Metallurgique des Terres Rares, Centre National de la Recherche Scientifique, GLVT, 2-8, rue Henri Dunant, F-94320 Thiais, FRANCE; telephone +33 1 4978 1201; telefax +33 1 4978 1203; E. Alleno's e-mail alleno@glvt-cnrs.fr; C. Godart's e-mail godart@glvt-cnrs.fr. Key words: high-Tc cuprates, Pr oxides, XANES.

D. N. Aristov, "Superconducting Correlations in any Dimensionality." Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188350, RUSSIA; e-mail aristov@thd.pnpi.spb.ru; preprint also available at cond-mat@xxx.lanl.gov (#9807381). 74.20.Fg; 74.90.+n; 05.30.Fk.

A. Badia, C. Lopez, and J. L. Giordano, "Optimal Control Model for the Critical State in Superconductors." To be published in Phys. Rev. B. Departamento de Fisica de la Materia Condensada, C.P.S.I. Universidad de Zaragoza, c/Maria de Luna 3, E-50015 Zaragoza, SPAIN; e-mail anabadia@posta.unizar.es.

A. V. Balatsky and R. Movshovich, "Marginal Stability of d-Wave Superconductor: Spontaneous P and T Violation in the Presence of Magnetic Impurities." Preprint #LA-UR-98-2174; to be published in the Proc. of the Int. Conf. on Stripes, Lattice Instabilities, and High Tc Supercond., Rome, Italy, June 2-7, 1998. Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545; e-mail avb@lanl.gov; preprint also available at cond-mat@xxx.lanl.gov (#9805345). 74.62.Dh; 71.55.-i.

G. Balestrino, A. Crisan, S. Martellucci, P. G. Medaglia, A. Paoletti, and G. Petrocelli, "(BaCuO2)m/((Ca,Sr)CuO2)n Superlattices Grown by Pulsed Laser Deposition: Structural and Electrical Transport Properties." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Dipartimento di Scienze e Tecnologie Fisiche ed Energetiche, INFM-Universita di Roma "Tor Vergata", Via di Tor Vergata, I-00133 Roma, ITALY; telephone +39 6 7259 7221; telefax +39 6 7259 7145; e-mail balestrino@utovrm.it. Key words: high-temperature superconductivity, superlattices, pulsed laser deposition.

G. Balestrino, S. Martellucci, P. G. Medaglia, A. Paoletti, G. Petrocelli, and A. A. Varlamov, "Dependence of the Critical Temperature on n in (BaCuO2)2/(CaCuO2)n Superlattices." To be published in Phys. Rev. B. Dipartimento di Scienze e Tecnologie Fisiche ed Energetiche, INFM-Universita di Roma "Tor Vergata", Via di Tor Vergata, I-00133 Roma, ITALY; telephone +39 6 7259 7221; telefax +39 6 7259 7145; e-mail balestrino@utovrm.it. 74.80.Dm; 81.15.Fg; 74.25.Fy; 74.25.Ha.

Yunkyu Bang, "A Vertex Correction in the Gap Equation for the High Temperature Superconductors." Preprint #CNUPh-712. Department of Physics, Chonnam National University, Kwangju 500-757, KOREA; preprint also available at cond-mat@xxx.lanl.gov (#9807378). 74.20.Fg; 74.20.Mn.

Zoe H. Barber, El Hadi S. Sadki, Richard A. Doyle, Stephen J. Lloyd, and Mark G. Blamire, "Niobium Nitride/Aluminium Nitride Superlattices." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Department of Materials Science, University of Cambridge, Pembroke Street, Cambridge, UNITED KINGDOM; e-mail zb10@cam.ac.uk. Key words: multilayers, nitrides, stacked junctions, flux flow, irreversibility, transmission electron microscopy, electron energy loss spectroscopy.

D. N. Basov, B. Dabrowski, and T. Timusk, "An Infrared Probe of Transition from Superconductor to Non-Metal in YBa2(Cu1-xZnx)4O8." To be published in Phys. Rev. Lett. Department of Physics, University of California at San Diego, La Jolla, CA 92093-0319. 74.25.-q; 74.25.Gz; 74.25.Nf.

*Maamar Benkraouda and John R. Clem, "Critical Current from Surface Barriers in Type-II Superconducting Strips." Submitted to Phys. Rev. B. Contact John R. Clem, A517 Physics, Ames Laboratory-USDOE and Department of Physics, Iowa State University, Ames, IA 50011-3020; telefax (515) 294-0689; e-mail clem@ameslab.gov. *Revised title and text.

Y. Bruynseraede, G. Verbanck, M. J. Van Bael, K. Temst, and V. V. Moshchalkov, "Coupling Phenomena and Critical Currents in Superconducting/Magnetic Superlattices." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven, BELGIUM. Key words: proximity effect, magnetic films, critical fields, flux pinning.

L. Bulaevskii, A. E. Koshelev, and M. P. Maley, "Josephson Plasma Resonance as a Structural Probe of Vortex Liquid." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Center for Materials Science, Mail Stop K765, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 667-9243; telefax (505) 665-2992. Key words: vortex liquid, pancake, Josephson coupled layers, Josephson plasma resonance, columnar defects, interlayer correlations of pancakes.

X. W. Cao, Z. H. Wang, and K. B. Li, "Critical Current Density and Flux Pinning in Vortex Liquid Regime for YBa2Cu3O7-d Epitaxial Thin Films." To be published in Physica C. High Magnetic Field Laboratory, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, PEOPLE'S REPUBLIC OF CHINA. 74.60.Jg; 74.60.Ge; 74.76.-w.

Qijin Chen, Ioan Kosztin, Boldizsar Janko, and K. Levin, "Pairing Fluctuation Theory of Superconducting Properties in Underdoped to Overdoped Cuprates." Submitted to Phys. Rev. Lett. James Franck Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637; e-mail qchen@rainbow.uchicago.edu; preprint also available at cond-mat@xxx.lanl.gov (#9807414). 74.20.-z; 74.25.-q; 74.62.-c; 74.72.- h.

Noriko Chikumoto, Shinobu Ozawa, and Masato Murakami, "Effects of Oxygen on the Superconducting Properties of Nd1+xBa2-xCu3O7-d (0 <= x <= 0.4) Solid Solution." To be published in Appl. Supercond. (in press). Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 16-25 Shibaura 1-chome, Minato-ku, Tokyo 105- 0023, JAPAN.

O. Chmaiisem, J. D. Jorgensen, S. Short, A. Knizhnik, Y. Eckstein, and H. Shaked, "Scaling of Tc and CuO2 Plane Buckling in a 123 Superconductor." Submitted to Nature. Contact Janice Coble, Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telephone (630) 252-5497; telefax (630) 252-9595; e- mail coble@anl.gov.

C. W. Chu, "High Temperature Superconductivity: A Macroscopic View." Preprint #98:069; submitted to the Proc. of the Euroconf. on Polarons: Condensation, Pairing, Magnetism, Erice, Italy, June 9-17, 1998; to be published in J. Supercond. Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu. Key words: high-temperature superconductivity, materials, occurrence, mechanism.

Z. J. Deng, H. Zhang, N. Yoshikawa, U. Ghoshal, E. Fang, A. Flores, L. Zheng, S. R. Whiteley, and T. Van Duzer, "Memory-Processor Interface with Hybrid CMOS-RSFQ Technology." To be published in Appl. Supercond. (in press). Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720-1770.

A. Agliolo Gallitto and M. Li Vigni, "Harmonic Emission at Microwave Frequencies in YBa2Cu3O7 Single Crystals Near Tc." To be published in Physica C (in press). Contact M. Li Vigni, Istituto Nazionale per la Fisica della Materia, Unita di Palermo and Dipartimento di Scienze Fisiche e Astronomiche, Via Archirafi 36, I-90123 Palermo, ITALY; telephone +39 91 623 4207; telefax +39 91 616 2461; e-mail livigni@fisica.unipa.it. Key words: high-temperature superconductors, electromagnetic field response, nonlinear effects. 74.25.Nf; 74.20.De.

R. Gatt, T. Schmauder, S. Misra, B. Frazer, R. J. Kelley, M. Onellion, I. Vobornik, M. Zacchigna, F. Zwick, M. Grioni, and G. Margaritondo, "Superconducting Gap Symmetry and Doping in Bi2Sr2CaCu2O8+x." Contact M. Onellion, Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706; e-mail onellion@comb.physics.wisc.edu.

Haranath Ghosh, "Complex Order Parameter Symmetry and Thermal Conductivity." To be published in Europhys. Lett. Instituto de Fisica, Universidade Federal Fluminense, Campus da Praia Vermelha, Av. Litoranea s/n, 24210-340 Niteroi, Rio de Janeiro, BRAZIL; e-mail hng@if.uff.br; preprint also available at cond-mat@xxx.lanl.gov (#9807373). 74.25.Fy; 74.60.Ec; 74.25.Dw.

G. N. Glavee, R. D. Hunt, and M. Paranthaman, "Low Temperature Preparation of BaCeO3 and Ce0.75Zr0.25O2 Thin Films Using Sol-Gel Processing Techniques." To be published in Mater. Res. Bull. Contact M. Paranthaman, Chemical and Analytical Sciences Division, Bldg. 4500 South, MS-6100, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6100; telephone (423) 574-5045; telefax (423) 574-4939; e-mail p11@ornl.gov. Key words: inorganic compounds, thin films, sol-gel chemistry, x-ray diffraction.

F. Gollnik and M. Naito, "Doping Dependence of Normal and Superconducting State Transport Properties of Nd2-xCexCuO4+-y Thin Films." To be published in Phys. Rev. B. Lehrstuhl Experimentalphysik II, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen, GERMANY.

D. Groten, A. C. Wallast, G. J. Nieuwenhuys, J. A. Mydosh, and J. Aarts, "Superconducting Properties of Thin Films of CeRu2." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Kamerlingh Onnes Laboratorium, Leiden University, P.O. Box 9506, 2300 RA Leiden, THE NETHERLANDS; e-mail groten@rulkol.leidenuniv.nl. Key words: superconductivity, thin films, flux line pinning, vortex lattice melting.

A. Gurevich and J. McDonald, "Nonlinear Current Flow Around Defects in Superconductors." To be published in Phys. Rev. Lett. Applied Superconductivity Center, University of Wisconsin-Madison, Madison, WI 53706; telephone (608) 263-2549; telefax (608) 263-1087; e-mail agourevi@facstaff.wisc.edu. 74.60.Ge.

J. Halbritter, "Charge Dynamics via the Blocking Layer of High-Tc Superconductors (HTS)." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Institut fuer Materialforschung I, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, GERMANY.

Nobuhiko Hayashi, Masanori Ichioka, and Kazushige Machida, "Relations Between Vortex Core Charge and Vortex Bound States." Submitted to J. Phys. Soc. Jpn. Department of Physics, Okayama University, Okayama 700- 8530, JAPAN; telefax +81 86 251 7830; e-mail hayashi@mp.okayama-u.ac.jp; preprint also available at cond-mat@xxx.lanl.gov (#9807253). Key words: vortex core, electric charge, vortex bound states, Bogoliubov-de Gennes theory, scanning tunneling microscopy.

Ryusuke Ikeda and Kiyoshi Isotani, "Ground States and Vortex Orderings in Fields Parallel to Layers of a Layered Superconductor." Department of Physics, Kyoto University, Kyoto 606-8502, JAPAN; e-mail ikeda@ton.scphys.kyoto-u.ac.jp. Key words: type-II superconductor, vortex states, superconducting fluctuation.

Q. D. Jiang, Z. J. Huang, A. Brazdeikis, L. M. Dezaneti, C. L. Chen, P. Jin, C. W. Chu, and J. Zegenhagen, "Microscopic Structure of SrTiO3 Bicrystal Boundaries Studied with Scanning Tunneling and Atomic Force Microscopy." Preprint #98:067; to be published in J. Mater. Sci. and Eng. 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. 61.16.Ch; 61.72.Mm; 68.35.-p; 68.35.Ct; 68.35.Bs.

J. R. Kirtley, V. G. Kogan, J. R. Clem, and K. A. Moler, "Magnetic Field of an In-Plane Vortex Outside a Layered Superconductor." Submitted to Phys. Rev. B. IBM Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598; telephone (914) 945-2043; telefax (914) 945- 4421; e-mail kirtley@watson.ibm.com; preprint also available at cond-mat@xxx.lanl.gov (#9808096).

R. A. Klemm, C. T. Rieck, and K. Scharnberg, "Angular Dependence of the Josephson Critical Current Across c-Axis Twist Junctions of Layered Superconductors." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; e-mail klemm@anl.gov. Key words: superconductivity, Josephson junctions, order parameter symmetry, critical currents.

T. Koyama, M. Machida, and M. Tachiki, "I-V Characteristics and Longitudinal Josephson Plasma in Intrinsic Layered Superconductors." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-77, JAPAN; telephone +81 22 227 6200; telefax +81 22 264 7984.

Raphael A. Lehrer and David R. Nelson, "Vortex Pinning and the Non- Hermitian Mott Transition." Lyman Laboratory of Physics, Harvard University, Cambridge, MA 02138; preprint also available at cond-mat@xxx.lanl.gov (#9806016).

M. Letz, "The Attractive Hubbard Model in 2D: Is It Capable of Describing a Pseudogap and Preformed Pairs?" To be published in J. Supercond. Institut fuer Physik, Johannes-Gutenberg Universitaet, Staudinger Weg 7, D-55099 Mainz, GERMANY; telephone +49 61 31 394214; telefax +49 61 31 395441; e-mail letz@anderson.physik.uni-mainz.de; Web site http://www.cond-mat.physik.uni-mainz.de/~letz/; preprint also available at cond-mat@xxx.lanl.gov (#9807383). Key words: negative-U Hubbard model, two-particle bound states, pseudogap, non Fermi-liquid properties. 74.20.Mn; 74.25.-q; 74.25.Fy; 74.25.Nf; 74.72.-h; 74.20.-z.

M. Letz and R. J. Gooding, "A Self-Consistent, Conserving Theory of the Attractive Hubbard Model in Two Dimensions." To be published in J. Phys.: Cond. Mat. Institut fuer Physik, Johannes-Gutenberg Universitaet, Staudinger Weg 7, D-55099 Mainz, GERMANY; telephone +49 61 31 394214; telefax +49 61 31 395441; e-mail letz@anderson.physik.uni-mainz.de; Web site http://www.cond-mat.physik.uni-mainz.de/~letz/. 74.20.Mn; 74.25.-q; 74.25.Fy; 74.25.Nf; 74.72.-h; 74.20.-z.

W. Vincent Liu, "Parity Breaking and Phase Transition Induced by a Magnetic Field in Superconductors." Preprint #UTTG-12-98. Theory Group, Department of Physics, University of Texas, Austin, TX 78712- 1081; telephone (512) 471-3898; telefax (512) 471-4888; e-mail liu@physics.utexas.edu; preprint also available at cond-mat@xxx.lanl.gov (#9808134). 11.30.Qc; 11.30.Er; 74.25.Dw.

Susanne Lomatch, "Theory and Application of Josephson-Coupled Multilayers as Switching Devices in Superconducting Electronics." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Department of Electrical and Computer Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3118. Key words: layered superconductors, Josephson-coupled multilayers, electronic switching.

Igor F. Lyuksyutov and Valery Pokrovsky, "Magnetism Coupled Vortex Matter." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Department of Physics, Texas A&M University, College Station, TX 77843-4242. Key words: magnetic dots, superconducting films, flux lines.

K. Maki and E. Puchkaryov, "Impurity Scattering in Isotropic p-Wave Superconductors." To be published in Europhys. Lett. Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484. 74.20.-z; 74.25.Bt; 74.25.Fy.

Kazumi Maki, E. Puchkaryov, and Hyekyung Won, "d-Wave Superconductivity in kappa-(BEDT-TTF))2Cu(NCS)2." To be published in Synthetic Metals. Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484. Key words: magnetotransport, unconventional superconductors, organic superconductors.

L. Maritato, C. Attanasio, S. Barbanera, C. Coccorese, T. Di Luccio, L. V. Mercaldo, S. L. Prischepa, R. Russo, and M. Salvato, "Pinning Forces in Nb/CuMn Multilayers." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Dipartimento di Fisica and INFM, Universita degli Studi di Salerno, Baronissi (Sa), ITALY; telefax +39 89 953804; e-mail maritato@vaxsa.csied.unisa.it. Key words: multilayers, pinning forces.

A. S. Mel'nikov, "Quasiparticle Spectrum Near the Gap Node Directions in the Mixed State of d-Wave Superconductors." Institute for Physics of Microstructures, Russian Academy of Sciences, Nizhny Novgorod 603600, GSP-105, RUSSIA; e-mail melnikov@ipm.sci-nnov.ru; preprint also available at cond-mat@xxx.lanl.gov (#9806188).

L. V. Mercaldo, C. Attanasio, and L. Maritato, "Systematic Analysis of the Critical Temperature Oscillations in Superconducting (Nb)/Spin-Glass (CuMn) Multilayers." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742-4111; L. Maritato's telefax at Baronissi, Italy +39 89 953804; e-mail maritato@vaxsa.csied.unisa.it. Key words: superconducting/ferromagnetic multilayers, proximity effect, Tc oscillations, pi phase.

V. Metlushko, U. Welp, G. Crabtree, Zhao Zhang, S.R.J. Brueck, B. Watkins, L. E. DeLong, B. Ilic, K. Chung, and P. J. Hesketh, "Periodic Arrays of Pinning Centers in Thin Vanadium Films." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Contact Janice Coble, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telefax (708) 252-9595; e-mail janice_coble@qmgate.anl.gov. Key words: superconductivity, thin films, pinning centers.

O. V. Misochko and G. Gu, "Electronic Raman Scattering in Disordered Bi2Sr2Ca(Cu1-xFey)2Od: Impurity Scattering Effects." Submitted to Phys. Rev. Lett. Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, RUSSIA; e-mail misochko@issp.ac.ru. 74.25.Gz; 74.72.Hs; 74.62.Dh.

S. Misra, R. Gatt, T. Schmauder, Andrey V. Chubukov, M. Onellion, M. Zacchigna, I. Vobornik, F. Zwick, M. Grioni, G. Margaritondo, C. Quitmann, and C. Kendziora, "Evolution of the Quasiparticle Spectral Function in Cuprates." To be published in Phys. Rev. B. (in press). Contact M. Onellion, Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706; e-mail onellion@comb.physics.wisc.edu; preprint also available at cond-mat@xxx.lanl.gov (#9805297).

J. Mosqueira, S. R. Curras, C. Carballeira, Th. Siebold, C. Torron, J. A. Campa, M. V. Ramallo, I. Rasines, and Felix Vidal, "In-Plane Magnetoresistivity Anomalies Near the Average Superconducting Transition in YBa2Cu3O7-d and Bi2Sr2CaCu2O8 Crystals with Non-Uniformly Distributed Tc Inhomogeneities." To be published in Supercond. Sci. & Technol. Laboratorio de Bajas Temperaturas y Superconductividad, Departamento de Fisica de la Materia Condensada, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, SPAIN; Felix Vidal's telephone +34 81 563100, ext. 14019, 14031, or 14023; telefax +34 81 531682; e-mail fmvidal@usc.es. 74.25.Fy; 74.62.-c; 74.72.-h.

C. Mueller, P. Majewski, S. Klaumuenzer, and F. Aldinger, "Flux Pinning by Columnar Defects in Bi2Sr2CaCu2O8+d Single Crystals and Annealing Effects." To be published in Nuclear Instrum. and Methods in Phys. Res.: Proc. of the 4th Int. Conf. on Swift Heavy Ions in Matter (SHIM '98), Berlin, Germany, May 11-15, 1998. Pulvermetallurgisches Laboratorium, Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 5, D-70569 Stuttgart, GERMANY; telefax +49 711 6861 131; e-mail cmueller@aldix.mpi-stuttgart.mpg.de.

Terukazu Nishizaki, Tomoyuki Naito, and Norio Kobayashi, "Anomalous Magnetization and Field-Driven Disordering Transition of Vortex Lattice in Untwinned YBa2Cu3Oy." To be published in Phys. Rev. B. Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, JAPAN; telephone +81 22 215 2029; telefax +81 22 215 2026; e-mail terukazu@imr.tohoku.ac.jp. 74.60.Ec; 74.60.Ge; 74.60.Jg; 74.72.Bk.

Yu. N. Ovchinnikov and V. Z. Kresin, "Non-Stationary State of Superconductors: Application to Nonequilibrium Tunneling Detectors." To be published in Phys. Rev. B. Lawrence Berkeley Laboratory, 1 Cyclotron Road, Berkeley, CA 94720.

L. Ozyuzer, John. F. Zasadzinski, Chris Kendziora, and K. E. Gray, "Tunneling Spectroscopy of Overdoped Bi2Sr2CaCu2O8+d Single Crystals." Submitted to Phys. Rev. B. Contact Janice Coble, Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telephone (630) 252-5497; telefax (630) 252-9595; e-mail coble@anl.gov; preprint also available at cond-mat@xxx.lanl.gov (#9807389). 74.50.+r; 74.80.Fp; 74.72.Hs; 74.62.Dh.

M. Paranthaman and B. C. Chakoumakos, "Synthesis and Characterization of Bulk HgBa2Can-1CunO2n+2+d (n=1,2,3,4) Superconductors." To be published in Studies of High Temp. Supercond., Vol. 26-27, edited by A. Narlikar (Nova Science Publishers, New York, 1998). Chemical and Analytical Sciences Division, Bldg. 4500 South, MS-6100, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6100; telephone (423) 574-5045; telefax (423) 574-4939; e-mail p11@ornl.gov.

M. Paranthaman and B. C. Chakoumakos, "Synthesis and Characterization of the Superconducting Quaternary Intermetallic Compound YNi2B2C: A Review." To be published in Studies of High Temp. Supercond., Vol. 26- 27, edited by A. Narlikar (Nova Science Publishers, New York, 1998). Chemical and Analytical Sciences Division, Bldg. 4500 South, MS-6100, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6100; telephone (423) 574-5045; telefax (423) 574-4939; e-mail p11@ornl.gov.

M. Paranthaman, F. A. List, D. F. Lee, A. Goyal, R. Feenstra, D. P. Norton, C. Park, D. T. Verebelyi, D. K. Christen, P. M. Martin, E. D. Specht, and D. M. Koreger, "Fabrication of High Current YBa2Cu3O7-y Coated Conductors Using Rolling-Assisted Biaxially Textured Substrates." Submitted to the Proc. of the 9th World Ceramic Congress and Forum on New Mater. (CIMTEC'98), Florence, Italy, June 14-19, 1998. Chemical and Analytical Sciences Division, Bldg. 4500 South, MS-6100, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6100; telephone (423) 574-5045; telefax (423) 574-4939; e-mail p11@ornl.gov.

M. Paranthaman, S. S. Shoup, D. B. Beach, J. S. Morrell, A. Goyal, E. D. Specht, J. E. Mathis, D. T. Verebelyi, and D. K. Christen, "Growth of Textured Buffer Layers and Superconductors on Rolled-Ni Substrates Using Sol-Gel Alkoxide Precursors." Submitted to the Proc. of the 9th World Ceramic Congress and Forum on New Mater. (CIMTEC'98), Florence, Italy, June 14-19, 1998. Chemical and Analytical Sciences Division, Bldg. 4500 South, MS-6100, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6100; telephone (423) 574-5045; telefax (423) 574-4939; e-mail p11@ornl.gov.

Wan Kyu Park, Su Youn Lee, and Zheong G. Khim, "Transport Properties of YBa2Cu3O7-d/PrBa2Cu3O7-d Superlattices." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Department of Physics, Seoul National University, Seoul 151-742, KOREA. Key words: high-temperature-superconductor superlattice, YBCO/PBCO superlattice, Kosterlitz-Thouless transition, Bardeen-Stephen model, current-voltage characteristics, vortex-antivortex pairs, flux-flow noise.

I.F.G. Parker, C. E. Gough, M. Endres, P. J. Thomas, G. Yang, and A. Yurgens, "Observation of Normal and Superconducting State Energy Gap Features from Intrinsic c-Axis Interlayer Tunneling in Bi2Sr2CaCu2O8 Crystals." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Superconductivity Research Group, University of Birmingham, Edgbaston, Birmingham B15 2TT, UNITED KINGDOM; C. Gough's e-mail c.gough@bham.ac.uk. Key words: HTc superconductor, Bi2Sr2CaCu2O8, c-axis properties, intrinsic Josephson tunnelling, normal state, pseudogap, non-equilibrium.

V. Polushkin, D. Glowacka, R. Hart, and John Lumley, "Effect of an Input Coil Microwave Resonance on Dynamics and Noise Properties of a dc Superconducting Quantum Interference Device Operating Close to the Hysteretic Mode." Oxford Instruments, Scientific Research Division, Newton House, Cambridge Business Park, Cowley Road, Cambridge CB4 4WZ, UNITED KINGDOM; telephone +44 1223 427400; telefax +44 1223 425050; Web site http://www.oxinst.com/.

A. I. Posazhennikova and M. V. Sadovskii, "Ginzburg-Landau Expansion in a Toy Model of Superconductor with Pseudogap." Institute for Electrophysics, Ural Branch of the Russian Academy of Sciences, 620049 Ekaterinburg, RUSSIA; e-mail posazhen@ief.uran.ru; M. V. Sadovskii's e- mail sadovski@ief.uran.ru; preprint also available at cond-mat@xxx.lanl.gov (#9806199). 74.20.Fg; 74.20.De.

Ch. Preis, Ch. Helm, J. Keller, A. Sergeev, and R. Kleiner, "Coupling of Intrinsic Josephson Oscillations in Layered Superconductors by Charge Fluctuations." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg, GERMANY; e-mail christian.preis@physik.uni-regensburg.de. Key words: intrinsic Joesphson effect, cuprate superconductors, plasma oscillations, c-axis current-voltage characteristics, non-linear dynamics.

S. L. Prischepa, V. N. Kushnir, A. Y. Petrov, C. Attanasio, and L. Maritato, "Pinning in Superconducting-Normal Metal Superlattices." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). State University of Informatics and RadioElectronics, P. Brovka 6, Minsk 220600, BELARUS; telephone +375 172 398 939; telefax +375 172 310 914; e-mail pslbel@rei.minsk.by. Key words: proximity effect, vortex lattice, peak effect, Ginzburg-Landau equations.

J. Rieger, M. Leghissa, J. Wiezorech, H.-P. Kraemer, G. Ries, and H.-W. Neumueller, "Development of a 10 m Long Superconducting Multistrand Conductor for Power Transmission Cables." To be published in Supercond. Sci. & Technol. Siemens AG, Corporate Technology, P.O. Box 3220, D- 91050 Erlangen, GERMANY; telephone +49 9131 7 34889; telefax +49 9131 7 33323; e-mail juergen.rieger@erls.siemens.de.

A. Schilling, R. A. Fisher, N. E. Phillips, U. Welp, W. K. Kwok, and G. W. Crabtree, "Angular Dependence of the Latent Heat of Vortex-Lattice Melting in Untwinned YBa2Cu3O7-d." To be published in Phys. Rev. B. Physik Institut, Universitaet Zurich, Winterthurerstrasse 190, CH-8057 Zurich, SWITZERLAND; telephone +41 1 635 5803; telefax +41 1 635 5704; e-mail schillin@physik.unizh.ch. 74.25.Bt; 74.60.Ge; 75.30.Gw.

Kentaro Setsune, Akihiro Odagawa, Masahiro Sakai, and Hideake Adachi, "I-V Characteristics and Formation of Single Josephson Junction Using the Intrinsic Layer in Bi-2223 Thin Films." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Central Research Laboratories, Matsushita Electric Industrial Co., Ltd., 3-4 Hikaridai, Seika-cho, Soraku, Kyoto 619-02, JAPAN; telefax +81 774 98 2585; e-mail setsu@crl.mei.co.jp.

A. Sherman and M. Schreiber, "Pseudogaps and Magnetic Properties of the Two-Dimensional t-J Model." Institut fuer Physik, Technische Universitaet, D-09107 Chemnitz, GERMANY; telephone +49 371 531 3145; telefax +49 371 531 3143; e-mail sherman@physik.tu-chemnitz.de; preprint also available at cond-mat@xxx.lanl.gov (#9808087).

Jun'ichi Shiraishi, Mahito Kohmoto, and Kazumi Maki, "Rhombic Vortex Lattice in d-Wave Superconductivity." To be published in Symmetry and Pairing in Supercond., edited by M. Ausloos and S. Kruchinin (Kluwer, Dordrecht, 1998): Proc. of the NATO Adv. Res. Workshop, Yalta, Crimea, Ukraine, April 28-May 2, 1998. Institute for Solid State Physics, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, JAPAN.

P. Silvestrini, B. Ruggiero, C. Granata, M. Russo, and V. G. Palmieri, "Energy Levels Quantization in Josephson Junctions." To be published in Appl. Supercond. (in press). Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, I-80125 Napoli, ITALY.

K. P. Sinha, "A Combined Mechanism Mediated by Lochons and Phonons for Cuprate Superconductors." To be published in Mod. Phys. Lett. B. Department of Physics, Indian Institute of Science, Bangalore 560 012, INDIA.

Y. N. Tsay, Qiang Li, Y. Zhu, M. Suenaga, G. D. Gu, and N. Koshizuka, "Electromagnetic and Microstructural Properties of Pure c-Axis Twist Bi2Sr2CaCu2O8+d Bicrystal Junctions." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Contact Qiang Li, Department of Applied Science, Brookhaven National Laboratory, Upton, NY 11973; telephone (516) 344-4490; telefax (516) 344-4071; e-mail qiangli@bnl.gov. Key words: bicrystal, Bi2Sr2CaCu2O8+d, c-axis twist, Josephson junction, critical current, misorientation angle.

J. L. Vicent, E. M. Gonzalez, J. I. Martin, and M. Velez, "Interplay Between Artificially Induced and Intrinsic Anisotropies in 123 Superconducting Superlattices." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). Departamento de Fisica de Materiales, Facultad Ciencias Fisicas, Universidad Complutense, E-28040 Madrid, SPAIN. Key words: superlattices, dimensionality, anisotropy, critical current, resistivity.

I. Vobornik, M. Zacchigna, F. Zwick, G. Margaritondo, M. Grioni, D. Poirier, C. G. Olson, C. Kendziora, R. Gatt, T. Schmauder, B. Frazer, S. Misra, R. J. Kelley, and M. Onellion, "Electronic Structure of Overdoped Bi2Sr2CaCu2O8+x." Contact M. Onellion, Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706; e- mail onellion@comb.physics.wisc.edu.

X. L. Wang, M. Ionescu, J. Horvat, X. Z. Liao, H. K. Liu, and S. X. Dou, "Comparative Studies of the Fishtail Effect Associated with Surface Pinning and Oxygen Vacancy Network in Spiral and Layer-by-Layer Grown Bi2Sr2CaCu2Oy Single Crystals." Presented at the Int. Symp. on Processing and Critical Currents of HTS, Wagga Wagga, Australia, Feb. 2- 4, 1998; to be published in Supercond. Sci. & Technol. Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522, AUSTRALIA; telephone +61 2 4221 5730; telefax +61 2 4221 5731; S. X. Dou's e-mail shi_dou@uow.edu.au.

Kazuo Watanabe, Satoshi Awaji, Mistuhiro Motokawa, Yukio Mikami, Junji Sakuraba, and Keiichi Watazawa, "15 T Cryocooled Nb3Sn Superconducting Magnet with a 52 mm Room Temperature Bore." To be published to Jpn. J. Appl. Phys. Lett. Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980, JAPAN; telephone +81 22 227 6200; telefax +81 22 264 7984. Key words: Nb3Sn, Bi2Sr2Ca2Cu3O10, cryocooled superconducting magnet, high-Tc current lead, high magnetic field.

J. G. Wen, T. Usagawa, H. Zama, Y. Enomoto, T. Morishita, and N. Koshizuka, "Microstructures of RE(RE:Y,Pr)Ba2Cu3Oy Films Grown on (001), (100) and (110) Oriented YBa2Cu3Oy Single Crystal Substrates." To be published in Appl. Supercond. (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: YBCO, homoepitaxy, TEM, single crystal.

Gary A. Williams, "Vortex Loop Phase Transitions in Liquid Helium, Cosmic Strings, and High-Tc Superconductors." Submitted to Phys. Rev. Lett. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095; e-mail gaw@ucla.edu; preprint also available at cond-mat@xxx.lanl.gov (#9807338).

H. Won and K. Maki, "Day of Unconventional Superconductors." Presented at the Proc. of the NATO Adv. Res. Workshop, Yalta, Crimea, Ukraine, April 28-May 2, 1998. Department of Physics and IRC, Hallym University, Chunchon 200-702, SOUTH KOREA. Key words: unconventional superconductor, d-wave superconductor, organic superconductor, superconducting fluctuation.

H. Wu, K. W. Dennis, M. J. Kramer, and R. W. McCallum, "Solubility Limits of LRE1+xBa2-xCu3O7+d." To be published in Appl. Supercond. (in press). Contact R. W. McCallum, Ames Laboratory-USDOE and Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011; telephone (515) 294-4736; telefax (515) 294-4291; e-mail mccallum@ameslab.gov.

X. Yao, E. Goodilin, Y. Yamada, H. Sato, and Y. Shiohara, "Crystal Growth and Superconductivity of Y1-xNdxBa2Cu3O7-d Solid Solutions." To be published in Appl. Supercond. (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.

Y. Zhang, N. Wolters, X. H. Zeng, J. Schubert, W. Zander, H. Soltner, H. R. Yi, M. Banzet, F. Rueders, and A. I. Braginski, "Washer rf SQUID Magnetometers with Coplanar Resonators at 77 K." To be published in Appl. Supercond. (in press). Institut fuer Schicht- und Ionentechnik (ISI), Forschungszentrum Juelich GmbH, D-52425 Juelich, GERMANY.

B. R. Zhao, B. T. Liu, Y. Lin, Z. Hao, E. Z. Luo, Z. Xie, L. H. Wilson, and B. Xu, "Growth and Features of High-Tc Superconducting Multilayers and Heterostructures." To be published in Superconducting Superlattices II: Native and Artificial, edited by I. Bozovic and D. Pavuna, SPIE Proc. 3480 (SPIE, Bellingham, 1998). National Laboratory of Superconductivity, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, PEOPLE'S REPUBLIC OF CHINA. Key words: superconductivity, ferroelectric, ultrathin film, multilayers, dimensionality, proximity effect, heterostructure, field effect.

H. Zheng, M. Jiang, R. Nikolova, V. Vlasko-Vlasov, U. Welp, B. W. Veal, H. Claus, and G. W. Crabtree, "Magnetization and Magnetic Levitation of Ring Samples Made of Melt Textured YBa2Cu3Ox." Submitted to Physica C. Contact Janice Coble, Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telephone (630) 252-5497; telefax (630) 252-9595; e-mail coble@anl.gov.

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

Oct. 18 - 21, 1998: China Magnets 98, Friendship Hotel, Beijing. Conference will cover supply, demand, innovations, markets for magnets, magnetic materials, and assemblies. Discussions on raw materials, processing, and applications. For information, contact Karen Zacharias, Gorham/Intertech Consulting, 411 US Route 1, Portland, ME 04105; telephone (207) 781-9800; telefax (207) 781-2150.

Dec. 4 - 7, 1998: Prof. K. S. Krishnan Birth Centenary Conference on Condensed Matter Physics, Allahabad University. Topics to be discussed in the conference are high-Tc superconductors and strongly correlated electron systems, semiconductors, alloys and defects, nanocrystals, dielectrics, ferroelectrics, surfaces and superlattices, disordered and glassy systems, etc. Abstract deadline, September 30, 1998; registration deadline October 15, 1998. For further information contact B. K. Agrawal, Conference Chair & Head of the Physics Department, Allahabad University, Allahabad 211 002, INDIA; telephone +91 532 608993; e-mail physics@nde.vsnl.net.in.

May 18 - 21, 1999: International Magnetics Conference (INTERMAG 99), Hotel Hyundai, Kyongju, Korea. Purpose is to provide a forum for presentation of new developments in applied magnetics, magnetic phenomena and materials, and information storage techniques. Contributed papers are solicited in related topics in all areas. Digests must be received by November 24, 1998. For information, contact INTERMAG 99, The Korean Magnetics Society, Rm. 905, The Korea Science and Technology Center, Yeoksam-dong 635-4, Kangnam-ku, Seoul 135-703, Korea; telephone +82 2 967 0518; e-mail intermag@kistmail.kist.re.kr; Web site http://intermag99.kist.re.kr/.

FYI
(High-Tc Update takes no responsibility for want ads listed in this section.)

Positions Open: Oxxel GmbH, a new company instituted on the campus of the University of Bremen, Germany, aims to advance atomic-layer engineering of complex oxides (including cuprate superconductors) as the platform technology for future oxide cryoelectronics. The research team will be led by Dr. Ivan Bozovic. Immediate openings are announced in the following areas: a) thin-film and heterostructure growth by ALL- MBE, developing and operating the MBE deposition system, monitoring growth by RHEED, characterizing the crystalline structure and morphology by XRD, AFM, SEM, TEM, etc.; b) film surface study by STM (cryogenic to high temperatures, ARUPS, HREELS, XRF, etc.); c) device and circuit design, lithographic mask design, device fabrication, and low- temperature electrical and magnetic measurements. The ideal candidate will have a recent Ph.D. from a top school in either physics, applied physics, materials science, or electrical engineering. Relevant experience is expected but apparent potential to reach and transcend the current technological frontiers is more important. Opportunity to operate unrivaled equipment to create new materials and devices, and to work in a free academic environment yet receive industrial wages. Opportunity to grow with the company. Language for communication is English; fluency in German is not required. Send CV and other relevant information to Oxxel GmbH, Technologiepark Universitaet, Fahrenheitstrasse 9, Bremen D-28359, Germany; telephone +49 421 20 46 6310; telefax +49 421 20 46 6350; e-mail info@oxxel.de.

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, #17, September 1, 1998