HIGH-Tc UPDATE E-MAIL VERSION, VOL. 13, NO. 6, March 15, 1999.

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.

The e-mail version of the High-Tc Update is sent to e-mail addresses accessible over INTERNET addresses. You can send e-mail messages to the editor at MITRA@AMESLAB.GOV or MITRA@IASTATE.EDU.

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 can be sent as an attachement (Word document). (This version preserves the Greek letters, special characters, accents, etc.) If you are interested in the the attached Word file instead of the ASCII text version, please contact the editor.

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: As announced in the last two issues in the newsletter, we will discontinue the free hard-copy version of the High-Tc Update newsletter beginning May 1, 1999, due to lack of funds. We will e-mail all our current hard-copy subscribers a PDF version of the newsletter. If you are interested in receiving this version of the newsletter instead of the Word or text version that you currently receive, please inform the office immediately. (If you receive both the e-mail and hard-copy versions of the newsletter, you will only receive the e-mail version beginning with the May 1 issue.)

Also, if you can help us with information regarding any funding opportunities that you believe may benefit High-Tc Update, please contact the editor! We certainly depend on you, our subscribers, for help.

Vortices

A preprint by M.J.W. Dodgson et al. (ETH-Zurich) establishes a new interstitial-vacancy-unbinding transition, which transforms the three- dimensional pancake vortex lattice of a decoupled layered superconductor into a defected solid. The authors stress that this transition is the natural finite-field extension of the vortex-antivortex unbinding transition establishing the zero-field superfluid transition. At finite Josephson coupling, the defect-unbinding transition turns into a topological decoupling transition.

A preprint by S. V. Kuplevakhsky (Kharkov State) claims to obtain the first exact analytical solution of the Lawrence-Doniach model for layered superconductors in external magnetic fields. The author's solution has some peculiar, unexpected features. The local magnetic field is independent of the coordinate perpendicular to the layers, such that Josephson vortices (oriented parallel to the layers) must penetrate into the sample simultaneously and coherently, aligning themselves in planes that are perpendicular to the layers. Extra constraints imposed by the author exclude solutions corresponding to single, isolated Josephson vortices. The author's theory thus contradicts not only numerous theoretical papers by previous authors but also experimental observations of in-plane Josephson vortices by scanning SQUID microscopy [e.g., K. A. Moler et al., Science 279, 1193 (1998)].

The vortex-state complex Hall conductivity sigma_[xy] of superconducting YBa2Cu3O7-d (YBCO) epitaxial films has been investigated by D. A. Beam (Caltech) et al. from dc to radio frequencies (up to 7 x 10^6 Hz) using a direct transport measurement technique. The authors analyzed their results with a generalized model assuming that: (a) the occurrence of the sign reversal in the dc vortex-state Hall conductivity is the result of different carrier densities inside and outside the vortex core, (b) the Drude approximation is applicable, and (c) the anomalous sign reversal occurs in the flux-flow limit. The magnetic field (B) dependence of the complex Hall conductivity data reveals that both vortices (sigma_[xy]^v) and quasiparticles (sigma_[xy]^q) contribute to the vortex-state Hall conduction, where sigma_[xy]^v proportional to B^[-1] and sigma_[xy]^q proportional to B, in agreement with the model.

The vortex-glass (VG) fluctuation contribution sigma_[xy]^[vg] to the Hall conductivity in the vortex-liquid regime of layered superconductors under a field perpendicular to the layers has been studied perturbatively by R. Ikeda (Kyoto), taking into account both line-like and point-like pinning. The author compared sigma_[xy]^[vg] with sigma_[xy]^[vf], the vortex-flow contribution to the Hall conductivity. For only line disorder, the author found that the ratio r_[gf] = sigma_[xy]^[vg]/sigma_[xy]^[vf] < 0, while in 3D-like systems with only point disorder, r_[gf] > 0. In the general case including both kinds of disorder, the sign of r_[gf] evidently depends upon both the relative amount of line-like and point-like disorder and the dimensionality of the thermal fluctuations.

The vortex-glass model for a disordered high-Tc superconductor in an external magnetic field has been studied by F. Pfeiffer (Koeln) and H. Rieger (Koeln and Juelich) in the strong-screening limit. With exact, numerical ground-state (T = 0) calculations, the authors found that (a) the ground state of the vortex configuration varies drastically with infinitesimal changes in the strength of the external magnetic field, (b) the minimum energy of global excitation loops of length scale L does not depend on the strength of the external field, but (c) the excitation loops themselves depend sensitively on the field. From (b), the authors infer the absence of a true superconducting state at any finite temperature, independent of the external field.

The dependence of the ohmic magnetoresistivity of clean twinned and detwinned YBa2Cu3O7-d single crystals upon temperature and field angle has been studied by R. M. Langan (Southampton) et al. The authors found that the thermodynamic properties of the vortex system are controlled by the effective field B_[eff] = B*epsilon_[theta], where epsilon_[theta] = (cos^2[theta] + epsilon^2sin^2[theta])^[1/2], B = mu_0H, theta is the angle of B relative to the c axis, and epsilon = gamma^[-1] = (m_[ab]/m_c)^[1/2] = 0.134 for YBa2Cu3O7-d. The authors found that the melting kink (a fingerprint of the first-order melting transition) is suppressed when the applied field is larger than the multicritical field B_[mc] but that this transition recovers when the sample is tilted at an angle theta such that B*epsilon_[theta] < B_[mc].

Transport and magnetic-relaxation measurements in the mixed state of strongly underdoped Y1-xPrxBa2Cu3O7-d crystals have been carried out by T. Stein (Kent State) et al. The authors observed a transition from thermally activated flux creep to temperature-independent quantum flux creep in both transport and magnetic relaxation at temperatures T <= 5 K. Flux-transformer measurements indicate that the crossover to quantum creep is preceded by a coupling transition. Based on these observations, the authors argue that below the coupling transition, the current is confined to a very thin layer, just a few unit cells thick, beneath the current contacts.

The distributions of vortices and antivortices in a superconducting slab after a sudden reversal of a parallel magnetic field have been studied theoretically by F. Bass (Bar-Ilan) et al. The authors find that structural defects can result in the creation of long-lived, spatially inhomogeneous, metastable flux-antiflux distributions.

Flux-noise spectra around the Kosterlitz-Thouless transition in a two- dimensional superconductor have been obtained by B. J. Kim and P. Minnhagen (Umea) from simulations of two-dimensional arrays of resistively shunted Josephson junctions. The authors investigated the dependence of the noise upon the distance d between the pickup coil and the sample. The authors identify features that distinguish between the large- and small-d limit, and they discuss the possibility of experimentally observing these features.

Hysteresis and ac Losses

Exact analytical results have been obtained by D. V. Shantsev (Oslo and St. Petersburg) et al. for the hysteretic magnetization of a superconducting thin strip with a general behavior Jc(B) of the critical current density. Using the critical state model with B = mu_0H, the authors show that the magnetization M of a strip as a function of applied field B_a has an extremum located exactly at B_a = 0. If Jc(B) decreases monotonically with B, the magnitude of the hysteretic magnetization will have a peak at B_[cp] = 0 in both decreasing and increasing magnetic fields. (This result differs from the behavior in a slab or cylinder in a parallel magnetic field, for which the magnitude of the magnetization has a peak at B_[cp] < 0 for the B_a-decreasing branch of the hysteresis loop, and a peak at B_[cp] > 0 for the field- increasing branch.) The authors find that this result is in excellent agreement with their experiments on an YBa2Cu3O7-d thin film. However, when artificial granularity is introduced by patterning the film, the central peak is shifted to B_[cp] > 0 on the field-decreasing branch of the hysteresis loop, and to B_[cp] < 0 for the field-increasing branch. These results show that a positive B_[cp] on the field-decreasing branch of the hysteresis loop is a definite signature of granularity in a thin- film superconductor.

A related paper by M. R. Koblischka (Oslo and SRL-ISTEC) et al. describes further details of magnetic flux penetration into an YBa2Cu3O7-d thin film patterned into a hexagonal-close-packed lattice of disks (diameter = 50 micrometers), which are touching each other at the circumference to enable the flow of an intergranular current. The authors had previously suggested such a sample as a model of a granular high-temperature superconductor. The magnetization of this sample exhibits a peak at B_[cp] > 0 on the field-decreasing branch of the hysteresis loop. Magneto-optical observations revealed that this peak is associated with magnetic flux trapped inside the disks.

The critical-state magnetic-field and current-density distributions in a thin superconducting platelet with elliptical shape in an increasing perpendicular applied magnetic field have been obtained approximately by G. P. Mikitik (Kharkov) and E. H. Brandt (MPI-Stuttgart) using the Bean model (Jc = const). In the limits of a circular disk or a long strip, the solutions are exact; i.e., the current density is constant in the region fully penetrated by magnetic flux. For ellipses with arbitrary axis ratio, the obtained current density is constant to typically 10^[- 3], and the magnetic moment deviates by less than 10^[-3] from the exact value. In increasing applied magnetic field, the penetrating flux fronts are approximately concentric ellipses whose axis ratio b/a <= 1 decreases and shrinks to zero when the flux front reaches the center, the long axis staying finite in the fully penetrated state. The authors present and discuss analytic expressions for these axes, the sheet current, magnetic moment, and perpendicular magnetic field. The authors' solution also applies to superconductors with anisotropic critical current if the anisotropy has a particular, but realistic form.

The ac losses and current distributions in a high-Tc superconducting layered conductor consisting of 15 thick-film Bi2Sr2CaCu2O8+d (Bi-2212) tapes in parallel, with interlayer insulation, have been investigated by H. Noji (IRC-Cambridge and Tsuruoka National College of Technology). The author used an electric-circuit model to calculate the ac electromagnetic properties of the conductor. The calculated and measured losses were found to be in good agreement in the high-current region.

Measurements and calculations of the real (chi') and imaginary (chi") parts of the ac magnetic susceptibility of a monofilamentary silver- sheathed Bi-2223 tape as a function of temperature (T = 4 K - 130 K), frequency (omega/2pi = 5 Hz - 5 kHz), and ac magnetic-field amplitude (mu_0H_m = 0.02 mT - 7 mT) are presented in a preprint by N. Savvides and K.-H. Mueller (CSIRO). The susceptibilities consist of a hysteretic component due to induced currents in the superconductor core and an eddy-current component due to induced eddy currents in the silver sheath. At low frequencies (< 50 Hz) and high temperatures, the measured chi" and hence ac loss per cycle are dominated by the hysteretic loss, which varies with amplitude but is essentially independent of frequency. At higher frequencies and low temperatures, the eddy-current loss of the silver sheath becomes dominant and increases with increasing frequency.

The dynamic resistance in a slab-like superconductor has been calculated by M. P. Oomen (Siemens) et al., taking into account a field-dependent critical current density Jc(B). In superconductors carrying a dc transport current in an ac external magnetic field, the dynamic resistance causes a transport loss that depends on the amplitude and frequency of this field, as well as on the transport current. At small field amplitudes and low transport currents, the model accurately predicts the dependence of the dynamic resistance upon field amplitude, field frequency, and transport current. For larger field amplitudes and higher transport currents, however, the resistance is found to be larger than the model predicts.

Voltages, voltage waveforms, and losses in hard superconductors carrying ac and dc transport current have been calculated by A. N. Ulyanov (Donetsk). The calculated results are in good agreement with experiment. The author explains the origin of a voltage-rectification effect for a superconductor carrying transport current I(t) = I_[dc] + I_[ac] cos(omega*t) as a consequence of the nonlinear current-voltage characteristics.

Bi Cuprates

A detailed compositional analysis of high-critical-current-density (Jc = 55 and 65 kA/cm^2 at 77 K) (Bi,Pb)2Sr2Ca2Cu3O10+d (Bi-2223) tapes has been undertaken by T. G. Holesinger (Los Alamos) et al. using energy- dispersive spectroscopy in the transmission electron microscope (TEM). The overall average composition of the Bi-2223 phase within the tapes was determined to be Bi1.88Pb0.23Sr1.96Ca1.95Cu2.98O10+d. However, spatial variations in the Bi-2223 composition and differing phase equilibria were found throughout the filament structure. In particular, the Pb content of the Bi-2223 phase was found to be significantly depressed in the vicinity of secondary and amorphous phases. The implications are that (a) different equilibrium conditions can exist on a local scale within the same tape, (b) the reaction kinetics can influence the final microstructure and prevent the system from reaching true chemical equilibrium, (c) the range of influence of the secondary phases is larger than their physical size, (d) a considerable range of Bi-2223 compositions can be found within a single tape, and (e) transport currents in Bi-2223 tapes must traverse or detour around boundaries separating regions of differing composition and phase content.

The critical current density Jc of Ag/(Bi,Pb)-2223 tapes in as-deformed and as-sintered states at various stages of tape processing has been studied by V. Beilin et al. (Hebrew University of Jerusalem). Intermediate pressing and rolling were found to result in significant I_c degradation. Bending tests showed that the I_c reduction was due to deformation-induced microcracks, which easily can be healed during the first hour of the next sintering. Intermediate deformation after the first sintering cycle was shown to significantly accelerate the 2212 to 2223 phase transformation during the first hours of the second sintering step. The authors found that I_c growth during the first hour of the second sintering step is not connected with the 2212 to 2223 transformation but is probably the result of increased pinning and structure-connectivity enhancement.

The in-plane and out-of-plane magnetoresistance of moderately overdoped Bi2Sr2CaCu2O8+d (Bi-2212) single crystals has been studied by G. Heine (Wien) et al. from Tc + 5 K to Tc + 100 K with the magnetic field oriented perpendicular and parallel to the current, respectively. The authors found that the in-plane magnetoresistance is positive, the out- of-plane magnetoresistance is negative, and their temperature variations depend on the orientation of the magnetic field. The authors applied a recent theory for superconducting order-parameter fluctuations to account for the interaction of carrier spins with the magnetic field. The authors found that the anomalous, anisotropic magnetoresistance can be described well by a unique set of physical parameters, which were found to agree with estimates from the normal-state transport properties.

La2-xSrxCuO4+d

The results of an angle-resolved photoemission (ARPES) study of La2- xSrxCuO4 (LSCO) from a slightly doped insulator (x = 0.03) to an optimally doped superconductor (x = 0.15) are reported by A. Ino (Tokyo) et al. As x increases, ARPES spectral weight is transferred between two components which coexist around the superconductor-insulator transition at x ~ 0.05, suggesting a microscopic inhomogeneity of the doped-hole distribution. For underdoped LSCO (x <= 0.1), the dispersive band crossing the Fermi level disappears in the (0,0)-(pi,pi) direction, unlike the behavior in Bi2Sr2CaCu2O8+d. The authors reconcile these observations with the evolution of holes in the insulator into fluctuating stripes in the superconductor.

Measurements of the penetration depths lambda_[ab](T) (H||c) and lambda_[perp.](T) (H perp. to c) in La1.85Sr0.15Cu1-xMxO4 for x = 0, 0.005, 0.01, 0.015, 0.025, and 0.035 for M = Ni and x = 0, 0.005, 0.01, and 0.02 for M = Zn have been carried out by A. J. Zaleski and J. Klamut (Wroclaw). The authors obtained the penetration depth from ac susceptibility measurements of powdered samples, immersed in wax, and magnetically oriented in a static magnetic field of 10 T. To understand the results, the authors suggest that both the effective mass and the density of charge carriers must be taken into account in theories describing high-temperature superconductivity.

Neutron-scattering measurements of spin-density-wave order within the superconducting state of a single crystal of predominantly stage-4 La2CuO4+y with a Tc(onset) of 42 K are reported by Y. S. Lee (MIT) et al. The low-temperature elastic magnetic scattering is incommensurate with the lattice and is characterized by long-range order in the copper- oxide plane with the spin direction identical to that in the insulator. Between neighboring planes, the spins exhibit short-range correlations with a stacking arrangement reminiscent of that in the undoped antiferromagnetic insulator. Within experimental error, the elastic magnetic peak intensity appears at the same temperature as the superconductivity, suggesting that the two phenomena are strongly correlated. The authors assert that these observations directly reveal the persistent influence of antiferromagnetic order as the doping level increases from the insulator to the superconductor. In addition, the results confirm that spin-density-wave order for incommensurabilities near 1/8 is a robust feature of the La2CuO4-based superconductors.

A preprint by F. Cordero (Roma) et al. reports combined anelastic and [139]^La NQR relaxation measurements that demonstrate the existence of relaxation-type dynamics of the O octahedra in La2CuO4. The combined data, which are in excellent agreement with each other, are interpreted in terms of soliton-like solutions of the one-dimensional equation of motion for the interacting octahedra, following a theoretical analysis by R. S. Markiewicz [Physica C 210, 264 (1993)]. On that basis, the authors propose a connection between the lattice excitations and the lattice stripes observed in La-based and Bi-based high-Tc superconductors.

Films

Measurements of mm-wavelength radiation from two-dimensional arrays of underdamped Nb/Al/AlOx/Nb Josephson junctions are reported by P. Barbara et al. (Maryland) [Phys. Rev. Lett. 82, 1963 (1999)]. The authors report that all of their samples emit coherently in a novel synchronized state, which is triggered by a resonance in the array structure. Measurements of the detected power as a function of the number N of active junctions show a threshold, suggesting population inversion. Above threshold, the power scales with N^2 up to an array size bigger than the free-space radiation wavelength. The highest measured conversion efficiency from dc to ac power is about 17%. The authors stress that their data are consistent with stimulated emission causing coherence and cannot be explained by existing classical coupling mechanisms.

The current in a clean superconductor/normal-metal/superconductor (S/N/S) junction of length d and width w in the presence of an applied magnetic field H has been studied theoretically by U. Ledermann et al. (ETH-Zurich). The authors show that both the geometrical pattern of the current density and the critical current I_c(Phi), where Phi is the total flux in the junction, depend on the ratio of the Josephson vortex separation a_0 = phi_0/Hd to the range r ~ (d*xi_N)^[1/2] of the nonlocal electrodynamics [phi_0 = hc/2e, xi_N = h[bar]v_F/2piT, and r(T-->0) ~ d]. In particular, the critical current has the periodicity of the superconducting flux quantum phi_0 only for r < a_0 and becomes, due to boundary effects, 2phi_0 (pseudo-) periodic for strong nonlocality, r > a_0. The authors find good agreement between their results and recent experiments by J. P. Heida et al. [Phys. Rev. B 57, R5618 (1998)].

The power-dependent microwave properties of a weak link in an YBa2Cu3O7- d thin film formed by writing a line of damage using a focused ion beam have been measured by A. Cowie (Imperial) et al. The measurements were made using a parallel-plate resonator at 5.5 GHz with the weak link written across the width of one of the plates. The ion-induced damage was characterized using a TRIM computer simulation, and the dc properties of similar weak links were measured. Using a 200 eV Si ion dose of 2 x 10^[13] cm^[-2], the Tc of the damaged region was reduced by 5.5 K and the normal resistivity was doubled. Surprisingly, the microwave measurements did not show any Josephson-junction characteristics. Rather, the ion-damaged region exhibited a greatly increased microwave resistivity, which was constant as a function of microwave power up to rf fields of 20 mT at 21 K.

Thermoelectric response times in the picosecond (ps) time domain have been observed by Th. Zahner et al. (Regensburg) in dynamical heating experiments with thin off-c-axis-grown YBa2Cu3O7-d films in the normal state. The thermoelectric response is due to the transverse Seebeck effect occurring in materials with anisotropic thermopower. Fast heating was accomplished by film irradiation with ps laser pulses, and response times of about 400 ps were observed for thin films of ~10 nm thickness at room temperature.

New phenomena manifesting nonequilibrium superconductivity induced by spin-polarized quasiparticles in perovskite ferromagnet/insulator/superconductor (F/I/S) heterostructures are reported by N.-C. Yeh (Caltech) et al. Measurements of the critical current density Jc, using a pulsed-current technique to minimize Joule heating, reveal a monotonic increase with increasing insulator thickness. For F/I/S with thin insulating barriers, a slight increase in Jc is observed under small injection currents I_m from the ferromagnet, followed by a strong suppression of Jc under large I_m. In contrast, no effect of injection on Jc was detected in an N/I/S control sample (N = nonmagnetic metal).

As reported by J.Y.T. Wei (Caltech) et al., scanning tunneling microscopy has been performed at 4.2 K on epitaxial thin-film YBa2Cu3O7- d/La0.7Ca0.3MnO3 heterostructures to study the microscopic effects of spin-polarized quasiparticle injection from the half-metallic ferromagnetic manganite on the high-Tc cuprate superconductor. The quasiparticle tunneling characteristics observed were consistent with d- wave pairing symmetry, with a gap maximum of Delta_0 ~~ 22 meV, up to at least 35 mA (7 x 10^3 A/cm^2) injection. Spectral smearing observed at higher injections could be fitted to elevated effective quasiparticle temperatures, although negligible sample heating was detected by in-situ thermometry. The overall spectral evolution with the injection current also appears to be nonthermal, showing a nonmonotonic change in both the zero-bias tunneling conductance and the area under the conductance spectrum.

A preprint by F. Taddei (Lancaster) et al. predicts that giant magnetoresistance (GMR) for current perpendicular to the plane (CPP) in a phase-coherent magnetic multilayer is suppressed when one of the contacts is superconducting. This is a consequence of a superconductivity-induced magnetoresistive (SMR) effect, whereby the conductance of the ferromagnetically aligned state is drastically reduced by superconductivity. To demonstrate this effect, the authors compute the GMR ratio of clean (Cu/Co)nCu and (Cu/Co)nPb multilayers, described by an ab-initio spd tight-binding Hamiltonian. By analyzing a simpler model with two orbitals per site, the authors also show that the suppression survives in the presence of elastic scattering by impurities.

A description of spin-polarized transport in mesoscopic ferromagnet/superconductor (F/S) systems where the transport is diffusive and the interfaces are transparent has been developed by F. J. Jedema et al. (Groningen). The authors show that the spin reversal associated with Andreev reflection generates an excess spin density close to the F/S interface, which leads to a spin contact resistance. Expressions for the contact resistance are given for two-terminal and four-terminal geometries. For the latter case, the sign depends on the relative magnetization of the ferromagnetic electrodes.

Applications

A YBCO thin-film rf SQUID has been fabricated by N. Khare (NPL) using a bicrystal junction. The YBCO film was deposited on a SrTiO3 36.8 degrees bicrystal substrate, and the rf SQUID structure was fabricated by a laser-patterning technique. The geometry consisted of one hole of dimension 50 x 10 micrometers^2 with two asymmetric bicrystal junctions of widths 5 micrometers and 20 micrometers. The rf SQUID operated in hysteretic mode, and its peak to peak amplitude of V-Phi oscillations was 60 microvolts at 77 K. The flux-noise density of the bicrystal junction rf SQUID was found to be 2 x 10^[-4] phi_0 Hz^[-1/2] at 2 Hz and 77 K.

Theory

A preprint by C. Honerkamp (ETH-Zurich) et al. compares different scenarios for the low-temperature splitting of the zero-energy peak in the local density of states at (110) surfaces of d_[x^2-y^2]-wave superconductors, observed by M. Covington et al. [Phys. Rev. Lett. 79, 277 (1997)]. Using a tight-binding model in the Bogoliubov-de Gennes treatment, the authors find a surface phase transition towards a time- reversal-symmetry-breaking, (s + id)-wave surface state carrying spontaneous currents. Alternatively, the authors show that electron correlation leads to a surface phase transition towards a magnetic state corresponding to a local spin-density-wave state.

A method to compute the exact density of states induced by N nonmagnetic impurities in a system of two-dimensional Dirac fermions in the unitarity limit is presented in a preprint by C. Pepin and P. A. Lee (MIT). The authors review the case of the pi-flux phase of the Heisenberg model and also treat the disordered d-wave superconductor. In both cases, the authors find additional states in the gap.

The effects of a magnetic field on the superconducting Tc and the spin pseudogap T* are discussed in a preprint by O. Zachar (Orsay). As a testable prediction, the author argues that a spin pseudogap should be observed in NMR experiments on overdoped samples in a magnetic field, even though there is no pseudogap above Tc in the absence of a magnetic field. The author finds that different theoretical approaches have marked differences in their predictions for overdoped high-Tc cuprates.

As noted in a preprint by Z. Y. Weng (TCSUH), underestimating the antiferromagnetic (AF) fluctuations in a fermionic resonating-valence- bond (RVB) state leads to an overestimate of the superconducting transition temperature Tc in the same system. The author points out that by starting with a bosonic RVB description where both the long- range and short-range AF correlations can be accurately described, the AF fluctuations can effectively reduce Tc to a reasonable value through the phase-string effect, by controlling the phase coherence of the superconducting order parameter.

Key features of antiferromagnetic dynamical correlations in high-Tc superconducting cuprates are discussed by Ph. Bourges (Saclay) et al. In the underdoped regime, the sharp resonance peak, occurring exclusively in the superconducting state, is accompanied by a broader contribution located around 30 meV, which remains above Tc. The authors suggest that the interplay of these features may induce incommensurate structure in the superconducting state.

A quantum Monte Carlo study of the thermodynamic properties of arrays of spin ladders with various widths, coupled via a weak interladder exchange coupling alpha*J, where J is the intraladder coupling both along and between the chains, has been carried out by Y. J. Kim (MIT) et al. This coupled-ladder system serves as a simplified model for the magnetism of presumed ordered spin and charge stripes in the two- dimensional CuO2 planes of hole-doped copper oxides. The authors discuss the implications of their results for the interpretation of neutron-scattering experiments on the dynamic spin fluctuations in La2- xSrxCuO4.

An efficient algorithm for obtaining the gauge-invariant gradient expansion of the local density of states and the free energy of a clean superconductor is presented in a preprint by L. Bartosch and P. Kopietz (Goettingen). The authors' method is based on a new mapping of the semiclassical linearized Gor'kov equations onto a pseudo-Schroedinger equation for a three-component wave function, where one component is directly related to the local density of states. Because this wave function satisfies a linear equation of motion, successive terms in the gradient expansion can be obtained by simple linear iteration. The authors confirm a recent calculation of the fourth-order correction to the free energy by I. Kosztin et al. [Phys. Rev. B 58, 9365 (1998)], who obtained a discrepancy with an earlier result by L. Tewordt [Z. Phys. 180, 385 (1964)]. The authors also give the fourth-order correction to the local density of states.

As noted in a preprint by I. I. Mazin and D. J. Singh (NRL), the Ru- based perovskites demonstrate an amazing richness in their magnetic properties, including 3D and quasi-2D ferromagnetism, antiferromagnetism, and unconventional superconductivity. The authors present first-principles calculations demonstrating that in both Ca2RuO4 and Sr2RuO4, ferromagnetic and antiferromagnetic fluctuations coexist, leading to an instability in Ca2RuO4 and to a close competition between p-wave and d-wave superconducting symmetries in Sr2RuO4.

On the basis of recent experiments, M. Sigrist (Kyoto) et al. argue that the symmetry of the superconducting phase of Sr2RuO4 is the odd-parity pairing state d(k) = z(k_x +- ik_y). The experimental evidence for this so-called orbital-dependent superconductivity leads to a single-band description of superconductivity based on a spin-fluctuation mechanism. The authors show that the state z(k_x +- ik_y) can be stabilized both by a spin-fluctuation feedback mechanism, as in the A phase of [3]^He, and by spin-orbit coupling effects.

Overviews

A lengthy review of the interplay of the electron-phonon interaction and strong correlations and its role in high-Tc superconductors (HTS) has been prepared by M. L. Kulic (Bayreuth and Bordeaux). The author argues that contrary to low-Tc superconductors (LTS), where the electron-phonon mechanism leads to s-wave pairing, strong electronic correlations in HTS renormalize the electron-phonon interaction in such a way that a forward scattering peak appears and backward scattering is suppressed. This leads to (a) a relative increase of the coupling constant for d-wave pairing, (b) a T-linear normal-state resistivity, (c) a suppression of scattering by nonmagnetic impurities, and (d) robustness of d-wave pairing in the presence of nonmagnetic impurities. For optimally hole- doped HTS, the forward scattering peak leads to a small isotope effect and strong temperature dependence of the gap anisotropy. For overdoped oxides, the forward scattering peak mechanism is suppressed, which leads to anisotropic s-wave pairing with moderate gap anisotropy and an increase of the isotope effect (393 refs.).

In a review by A. Houghton (Brown) et al., the authors outline an approach via bosonization to the problem of many interacting fermions in spatial dimensions greater than one. The authors stress the simplicity of the approach, as the virtue of multidimensional bosonization lies in the reduction of complicated four-fermion interactions to a Gaussian problem. The authors recover well-known results of Landau theory, and they test the limits of multidimensional bosonization by considering several examples of non-Fermi liquids, in particular the composite fermion theory of the half-filled Landau level (124 refs.).

A survey of current theoretical understanding of the statics and dynamics of the flux-line lattice in realistic geometries has been prepared by E. H. Brandt (MPI-Stuttgart). The author discusses phenomenological theories, flux-line-lattice statics, flux-line dynamics, geometry effects, and nonlinear and linear ac susceptibilities. The author also describes a numerical method by which the magnetic response of superconductors can be computed in any geometry (74 refs.).

An overview by A. I. Braginski (Juelich) characterizes the status of the superconducting electronics (SCE) market. The author discusses the degree of acceptance of SQUID magnetometers and susceptometers in magnetoencephalography (MEG), magnetocardiography (MCG), liver SQUID susceptometry, materials science, physical research, geomagnetic measurements, and nondestructive evaluation or testing (NDE, NDT); and he summarizes the potential role of SCE in analog filters for cellular telephony and in future analog components for wireless systems and satellite communications. The author notes that while rapid single flux-quantum (RSFQ) digital electronics has no market share today, it still has the largest long-term potential for a large market in telecommunications and massive data processing. The author also summarizes findings of a survey of 45 industrial organizations that have been involved in SCE by manufacturing products for the market, performing prototype trials with potential customers, or conducting pre- prototype R&D (58 refs.).

The experimental trends in a database of specific-heat measurements near Tc in high magnetic fields for type-II superconductors with a large value of kappa = lambda/xi, including mostly high-temperature superconductors, are considered in a paper by A. Junod et al. (Geneve). The authors present evidence from specific heat, scanning tunneling microscopy (STM), and other measurements that support the idea of a crossover near k_Fxi ~~ 1 from BCS-like superconductivity for weak coupling (k_Fxi >> 1) to Bose-Einstein-condensation-like (BEC-like) superconductivity for strong coupling (k_Fxi << 1) (55 refs.).

The technical status of high-temperature SQUID magnetometers and gradiometers has been reviewed by A. I. Braginski (Juelich) with emphasis on single-layer sensors currently used in applications. The author discusses the use of high-Tc SQUIDs for nondestructive evaluation and geomagnetic measurements, especially the exploration of mineral deposits. The author also presents selected highlights of recent developments with an emphasis on applications already implemented in practice or approaching that stage (53 refs.).

A brief overview of why a new mechanism and a many-body theory of superconductivity are required for the cuprates, which are doped correlated insulators, has been prepared by V. J. Emery (Brookhaven) and S. A. Kivelson (UCLA). The authors review the essential features of their approach, in which the physics is driven by the kinetic energy, and they summarize experimental support for such a theory (46 refs.).

A preprint by E. H. Brandt (MPI-Stuttgart) summarizes theoretical results for the complex magnetic ac susceptibility chi as a function of frequency omega and amplitude H_0 for various geometries, including thin-film disks, rings, and strips, and thicker platelets in a perpendicular magnetic field. The author discusses how the linear chi(omega) depends on the linear resistivity rho_[ac](omega) = E/J or penetration depth lambda_[ac](omega) and how the nonlinear chi(H_0,omega) depends on the nonlinear current-voltage law E(J,B) (45 refs.).

A chapter on ultrafast time-resolved optical spectroscopy in high- temperature superconductors has been prepared by D. Mihailovic and J. Demsar (Ljubljana). This method enables the direct real-time measurement of nonequilibrium quasiparticle recombination dynamics. The authors use experimental data and relevant theories to develop a consistent picture of the low-energy electronic structure in YBa2Cu3O7-d (26 refs.).

Contributed by John R. Clem

Contents: Preprints begin on page 7; Coming Events begin on page 14; 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.

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.

Priti Agarwala, M. P. Srivastava, P. N. Dheer, V.P.N. Padmanaban, and A. K. Gupta, "Enhancement in Tc of Superconducting BPSCCO Thick Films Due to Irradiation of Energetic Argon Ions of Dense Plasma Focus." To be published in Physica C (in press). Contact M. P. Srivastava, Department of Physics and Astrophysics, University of Delhi, New Delhi 110007, INDIA; telephone +91 11 7257793; telefax +91 11 7257061; e-mail csec@ern.doe.ernet.in. Key words: dense plasma focus, ion irradiation, BPSCCO superconducting film, superconducting transition temperature. 52.75.-d; 61.80.Jh; 74.76.-w.

M. Agop, C. Gh. Buzea, N. Rezlescu, C. Buzea, and C. Marin, "Wave Guide Perturbative Solutions for the Ginzburg-Landau Equation: Infinite Conductivity and Discrete Values of the Critical Temperature in Superconductors." To be published in Physica C (in press). Contact N. Rezlescu, Superconductivity Research Laboratory, Institute of Technical Physics, Bd. D. Mangeron 47, Iasi 6600, ROMANIA; telephone +40 32 130680; telefax +40 32 231132; e-mail reznic@phys-iasi.ro. Key words: wave guide, perturbative solutions, Ginzburg-Landau equation, infinite conductivity, superconductors. 74.20.De; 74.20.Mn; 74.62.Yb; 42.65.Wi.

T. Akao, S. Lee, N. Kiryakov, D. Emelyanov, H. Suematsu, and H. Yamauchi, "Single Crystal Study of Enchanced Flux Pinning in (Hg,Pb)(Ba,Sr)2Ca2Cu3O8+d and (Hg,Pb)Sr2Ca2Cu3O8+d." To be published in Advances in Supercond. XI: Proc. of the 11th Int. Symp. on Superconductivity (ISS'98), Fukuoka, Japan, Nov. 16-19, 1998; edited by N. Koshizuka and S. Tajima (Springer-Verlag, Tokyo). Contact H. Yamauchi, Materials & Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, JAPAN; telephone +81 45 924-5315; telefax +81 45 924-5365 or -5360; e-mail yamauchi@materia.titech.ac.jp. Key words: Hg-based superconductors, cation substitutions, single crystals, irreversibility lines, peak effect.

S. M. Ammirata, Mark Friesen, Stephen W. Pierson, LeRoy A. Gorham, Jeffrey C. Hunnicutt, M. L. Trawick, and C. D. Keener, "Dynamic Scaling for 2D Superconductors in Zero Magnetic Field." To be published in Physica C (in press). Contact Stephen W. Pierson, Department of Physics, Worcester Polytechnic Institute (WPI), 100 Institute Road, Worcester, MA 01609-2280; telephone (508) 831-5391; telefax (508) 831- 5886; e-mail pierson@wpi.edu. Key words: dynamic scaling, 2D superconductors, zero magnetic field, Kosterlitz-Thouless dynamics.

V.P.S. Awana, O. F. de Lima, S. K. Malik, W. B. Yelon, and A. V. Narlikar, "Structural and Superconducting Properties of LaBaCaCu3O7 System: A Neutron Diffraction Study." To be published in Physica C (in press). Instituto de Fisica 'Gleb Wataghin,' Universidade Estadual de Campinas (UNICAMP), 13083-970 Campinas, SP, BRAZIL; telefax +55 19 289 3137; e-mail awana@ifi.unicamp.br. Key words: high-Tc superconductors, chemical synthesis, crystal structure and symmetry, x-ray spectroscopy.

P. Barbara, A. B. Cawthorne, S. V. Shitov, and C. J. Lobb, "Stimulated Emission and Amplification in Josephson Junction Arrays." To be published in Phys. Rev. Lett. Center for Superconductivity Research, Department of Physics, University of Maryland at College Park, College Park, MD 20742-4111. 78.45.+h; 42.25.Kb; 85.25.Cp.

Lorenz Bartosch and Peter Kopietz, "An Efficient Algorithm for Obtaining the Gradient Expansion of the Local Density of States and the Free Energy of a Superconductor." Institut fuer Theoretische Physik, Universitaet Goettingen, Bunsenstrasse 9, D-37073 Goettingen, GERMANY; Peter Kopietz's e-mail kopietz@theorie.physik.uni-goettingen.de; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902042. 74.20.-z; 74.25.Bt.

F. Bass, G. Jung, B. Ya. Shapiro, and I. Shapiro, "Pinning Modulation of Flux-Antiflux Dynamics." To published in Physica C. Contact B. Ya. Shapiro, Institute of Superconductivity, Department of Physics, Bar-Ilan University, Ramat Gan 52900, ISRAEL. 74.60.Ge.

D. A. Beam, N.-C. Yeh, and R. P. Vasquez, "Vortex-State Complex Hall Conductivity of Superconducting YBa2Cu3O7-d Epitaxial Films at Radio Frequencies." Submitted to Phys. Rev. B. Contact N.-C. Yeh, Department of Physics, California Institute of Technology, Pasadena, CA 91125; e- mail ncyeh@caltech.edu. 74.60.Ge; 74.60.Ec; 74.25.Dw; 74.72.Bk.

Vladimir Beilin, Alexander Goldgirsh, Emanuel Yashchin, Michael Roth, and Michael Schieber, "Effects of Intermediate Deformation and Thermal Processing in the OPIT Process upon Critical Current Density of Ag/BiSSCO Tapes." To be published in IEEE Trans. Appl. Supercond.: Proc. of the 1998 Appl. Supercond. Conf. (ASC), Palm Desert, Calif., Sept. 13-18, 1998. Crystal Growth and Electronic Materials Laboratory, School of Applied Science, Bergman Bldg., Hebrew University of Jerusalem, Jerusalem 91904, ISRAEL; telephone +972 2-658 6414; telefax +972 2-658 6412 or -566 3878; e-mail beilin@shum.cc.huji.ac.il.

Ph. Bourges, Y. Sidis, H. F. Fong, B. Keimer, L. P. Regnault, J. Bossy, A. S. Ivanov, D. L. Milius, and I. A. Aksay, "Spin Dynamics in High-Tc Superconductors." To be published in the Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. Laboratoire Leon Brillouin, CEA-CNRS, CE Saclay, F-91191 Gif sur Yvette, FRANCE; e-mail bourges@bali.saclay.cea.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902067.

Alex I. Braginski, "Application of High-Temperature SQUID Magnetometers to Nondestructive Evaluation and Geomagnetic Exploration." To be published in Advances in Supercond. XI: Proc. of the 11th Int. Symp. on Superconductivity (ISS'98), Fukuoka, Japan, Nov. 16-19, 1998; edited by N. Koshizuka and S. Tajima (Springer-Verlag, Tokyo). Institut fuer Schicht- und lonentechnik (ISI), Forschungszentrum Juelich GmbH, D-52425 Juelich, GERMANY; telephone +49 2461 612330; telefax +49 2461 612333. Key words: superconductivity, SQUID, magnetometer, gradiometer, nondestructive testing, geomagnetism.

Alex I. Braginski, "Superconducting Electronics Coming to Market." To be published in IEEE Trans. Appl. Supercond.: Proc. of the 1998 Appl. Supercond. Conf. (ASC), Palm Desert, Calif., Sept. 13-18, 1998. Institut fuer Schicht- und lonentechnik (ISI), Forschungszentrum Juelich GmbH, D-52425 Juelich, GERMANY; telephone +49 2461 612330; telefax +49 2461 612333.

Ernst Helmut Brandt, "ac Response of Thin Film Superconductors at Various Temperatures and Magnetic Fields." Submitted to Phil. Mag.: Proc. of the 1st Intl. Workshop on Semicond. and Supercond. Mater., Turin, Italy, Feb. 17-19, 1999. Max Planck Institut fuer Metallforschung, P.O.B. 800665, D-70506 Stuttgart, GERMANY; telephone +49 711 689-1823; telefax +49 711 689-1010 or -1932; e-mail ehb@physix.mpi-stuttgart.mpg.de; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902187.

Ernst Helmut Brandt, "Statics and Dynamics of the Flux-Line Lattice in Realistic Geometries." To be published in Phys. and Mater. Sci. of Vortex States, Flux Pinning, and Dynamics: Proc. of the NATO Adv. Study Inst., Kusadasi, Turkey, July 26-Aug. 8, 1998; edited by R. Kossowsky, S. M. Bose, V. Pan, and H. Z. Durusoy (Kluwer, 1999). Max Planck Institut fuer Metallforschung, P.O.B. 800665, D-70506 Stuttgart, GERMANY; telephone +49 711 689-1823; telefax +49 711 689-1010 or -1932; e-mail ehb@physix.mpi-stuttgart.mpg.de.

A. Yu. Cherny and A. A. Shanenko, "Bound Pair States Beyond the Condensate for Fermi Systems Below Tc: The Pseudogap as a Necessary Condition." Submitted to Phys. Rev. B. Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, RUSSIA; e-mail cherny@thesun1.jinr.ru; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9901224. 74.20.-z; 05.30.Fk; 05.30.-d.

F. Cordero, R. Cantelli, M. Corti, A. Campana, and A. Rigamonti, "Tilt Waves Dynamics of the Oxygen Octahedra in La2CuO4 from Anelastic and [139]^La NQR Relaxation." To be published in Phys. Rev. B. Istituto di Acustica "O.M. Corbino," CNR, Area di Ricerca di Roma-Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome, ITALY; telephone +39 06 4993 4114; telefax +39 06 2066 0061; e-mail cordero@idac.rm.cnr.it; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902087.

A. Cowie, L. F. Cohen, and M. W. Denhoff, "The Microwave Power Handling of a FIB Generated Weak Link in a YBCO Film." Report NRC #42223; submitted to Supercond. Sci. & Technol. Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ, UNITED KINGDOM; M. W. Denhoff's e-mail at National Research Council, Canada denhoff@nrcphy1.phy.nrc.ca; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902109.

H. Deng, C. Dong, H. Chen, F. Wu, S. L. Jia, J. C. Shen, and Z. X. Zhao, "Structural Refinement of RE2ACu2O6 from Powder X-Ray Diffraction Data (RE=La,Nd; A=Sr,Ca)." To be published in Physica C (in press). National Laboratory for Superconductivity, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, PEOPLE'S REPUBLIC OF CHINA; telephone +86 10 6201 4488, ext. 3225; telefax +86 10 6237 6971; e-mail cdfzdhl@public.east.cn.net. Key words: superconductor, (La,Nd)-(Sr,Ca)-Cu-O system, 0212 phases, powder diffraction, Rietveld refinement.

Matthew J. W. Dodgson, Vadim B. Geshkenbein, and Gianni Blatter, "Defect-Unbinding Transition in Layered Superconductors." Institut fuer Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich, SWITZERLAND; telephone +41 1 633-2573 or -2570; telefax +41 1 633 1115; e-mail mattd@itp.phys.ethz.ch; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902244. 74.60.Ec; 74.60.Ge.

V. J. Emery and S. A. Kivelson, "Local Electronic Structure and High Temperature Superconductivity." To be published in the Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. Department of Physics, Brookhaven National Laboratory, Upton, NY 11973-5000; S. A. Kivelson's e-mail at University of California at Los Angeles stevek@physics.ucla.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902179.

N. M. Hamdan, Kh. A. Ziq, and A. S. Al-Harthi, "Effect of Fluorine on the Phase Formation and Superconducting Properties of Tl-1223 Superconductors." To be published in Physica C (in press). Department of Physics, King Fahd University of Petroleum and Minerals, Box 1487, Dhahran 31261, SAUDI ARABIA; telephone +966 3 860 2255; telefax +966 3 860 2293; e-mail nmhamdan@kfupm.edu.sa. Key words: fluorination, overdoped, Tl-1223, hole concentration. 74.10.+v.

G. Heine, W. Lang, X. L. Wang, and S. X. Dou, "Positive In-Plane and Negative Out-of-Plane Magnetoresistance in the Overdoped High- Temperature Superconductor Bi2Sr2CaCu2O8+x." To be published in Phys. Rev. B. Contact W. Lang, Ludwig Boltzmann Institut fuer Festkoerperphysik, Kopernikusgasse 15, A-1060 Wien, AUSTRIA; telephone +43 1 586 3408 21; telefax +43 1 586 3408 13; e-mail wolfgang.lang@univie.ac.at. 73.50.Jt; 74.40.+k; 74.72.Hs.

A. D. Hernandez, C. Hart, M. Acosta, and O. Ares, "Magnetic Field Dependence of the Critical Current in Polycrystalline YBCO Bridges with Decreasing Width." To be published in Physica C (in press). Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, Havana, CUBA; telefax +53 7 334247; e-mail supercon@fmq.uh.edu.cu. Key words: Josephson effect, granular superconductivity, weak couplings.

T. G. Holesinger, J. F. Bingert, M. Teplitsky, Q. Li, R. Parrella, M. P. Rupich, and G. N. Riley, Jr., "Spatial Variations in Composition in High-Jc Bi-2223 Tapes." Submitted to J. Mater. Res. MST-6, Metallurgy Group, Materials Science Division, MS G755, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 667-2911; telefax (505) 667-5268; e-mail holesinger@lanl.gov.

Carsten Honerkamp, Katsunori Wakabayashi, and Manfred Sigrist, "Instabilities at [110] Surfaces of d_[x^2-y^2] Superconductors." Institut fuer Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich, SWITZERLAND; e-mail chonerka@itp.phys.ethz.ch; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902026. 74.50.+r; 75.30.Pd; 74.72.Bk.

T. Hosomi, H. Suematsu, H. Fjellvag, M. Karppinen, and H. Yamauchi, "Identification of Superconducting Phases in the Ba-Ca-Cu-O System: An Unstable Phase with Tc ~~ 126 K and Its Derivative with Tc ~~ 90 K." To be published in J. Mater. Chem. Contact H. Yamauchi, Materials & Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, JAPAN; telephone +81 45 924-5315; telefax +81 45 924-5365 or -5360; e-mail yamauchi@materia.titech.ac.jp.

A. Houghton, H.-J. Kwon, and J. B. Marston, "Multidimensional Bosonization." Department of Physics, Brown University, Box 1843, Providence, RI 02912-1843; J. B. Marston's e-mail jbm@itp.ucsb.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9810388.

Ryusuke Ikeda, "Hall-Sign Dependent on Dimensionality of Vortex-Pinning Disorder." Department of Physics, Kyoto University, Kyoto 606-8502, JAPAN; e-mail ikeda@ton.scphys.kyoto-u.ac.jp.

A. Ino, C. Kim, M. Nakamura, T. Mizokawa, Z.-X. Shen, A. Fujimori, T. Kakeshita, H. Eisaki, and S. Uchida, "Electronic Structure of La2- xSrxCuO4 in the Vicinity of Superconductor-Insulator Transition." Submitted to Phys. Rev. Lett. Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, JAPAN; e-mail ino@wyvern.phys.s.u- tokyo.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond- mat/9902048. 74.25.Jb; 71.30.+h; 74.72.Dn; 79.60.-i; 74.62.Dh.

F. J. Jedema, B. J. van Wees, B. H. Hoving, A. T. Filip, and T. M. Klapwijk, "Spin Accumulation Induced Resistance in Mesoscopic Ferromagnet/Superconductor Junctions." Submitted to Phys. Rev. Lett. Department of Applied Physics and Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, THE NETHERLANDS; telephone +31 50 363 4919; telefax +31 50 363 3900; e-mail jedema@phys.rug.nl; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9901323.

Alain Junod, Andreas Erb, and Christophe Renner, "Specific Heat of High Temperature Superconductors in High Fields at Tc: From BCS to the Bose- Einstein Condensation." Presented at the First Crete Euroconference on Anomalous Complex Superconductors (ACS-1), Heraklion, Greece, Sept. 25- Oct. 2, 1998; to be published in Physica C. Departement de Physique de la Matiere Condensee, Universite de Geneve, 24 quai Ernest-Ansermet, CH- 1211 Geneva 4, SWITZERLAND; e-mail alain.junod@physics.unige.ch. Key words: high-temperature superconductors, specific heat at Tc, critical behavior, Bose-Einstein condensation.

Shin-ichi Karimoto and Michio Naito, "New Superconducting PbSr2CuO5+d Prepared by a Novel Low-Temperature Synthetic Route Using Molecular Beam Epitaxy." To be published in Jpn. J. Appl. Phys. NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, JAPAN; telephone +81 462 40-3558; telefax +81 462 40-2364 or -4717; e- mail karimoto@with.brl.ntt.co.jp. Key words: PbSr2CuO5+d, Pb-1201, high-Tc superconductor, thin films, MBE, homologous series, low- temperature synthesis, substrates.

Neeraj Khare, "YBCO Thin Film rf SQUID Using Bicrystal Junction." To be published in Physica C (in press). National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, INDIA; telefax +91 11 575 2678; e- mail nkhare@csnpl.ren.nic.in. Key words: rf SQUID, bicrystal junction, high-Tc superconductors.

Beom-Jun Kim and Petter Minnhagen, "Flux-Noise Spectra Around the Kosterlitz-Thouless Transition for Two-Dimensional Superconductors." Submitted to Phys. Rev. B. Department of Theoretical Physics, Umea University, 901 87 Umea, SWEDEN; e-mail kim@tp.umu.se; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902148. 74.40.+k; 74.76.-w; 74.50.+r.

Dong-Wook Kim, Dae-Ho Kim, Bo-Soo Kang, T. W. Noh, S. Shin, and Z. G. Khim, "Atomic Control of Homoepitaxial SrTiO3 Films Using Laser Molecular Beam Epitaxy." To be published in Physica C (in press). Department of Physics and Condensed Matter Research Institute, Seoul National University, Seoul 151-742, SOUTH KOREA; telephone +82 2 883 1385; telefax +82 2 875 1222; e-mail dwkim@phya.snu.ac.kr. Key words: homoepitaxial SrTiO3 film, oxygen annealing, step structure, laser molecular beam epitaxy, RHEED. 68.55.Jk; 81.15.Fg.

Y. J. Kim, R. J. Birgeneau, M. A. Kastner, Y. S. Lee, Y. Endoh, G. Shirane, and K. Yamada, "Quantum Monte Carlo Study of Weakly Coupled Spin Ladders." Center for Materials Science and Engineering, Room 13- 2122, Massachusetts Institute of Technology, Cambridge, MA 02139; e-mail ykim@yoko.mit.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902248.

M. R. Koblischka, L. Pust, A. Galkin, P. Nalevka, M. Jirsa, T. H. Johansen, H. Bratsberg, B. Nilsson, and T. Claeson, "Flux Penetration into an Artificially Granular High-Tc Superconductor." To be published in Phys. Rev. B. Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 1-16-25 Shibaura, Minato- ku, Tokyo 105, JAPAN; e-mail koblischka@istec.or.jp. 74.60.Ec; 74.60.Ge; 74.60.Jg; 74.80.Bj.

Hiroshi Kohno, Hidetoshi Fukuyama, and Manfred Sigrist, "Effects of Disorder on the Competition Between Antiferromagnetism and Superconductivity." Submitted to J. Phys. Soc. Jpn. Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, JAPAN; e-mail kohno@watson.phys.s.u-tokyo.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902089. Key words: superconductivity, antiferromagnetism, disorder, Ginzburg-Landau theory, CexCu2Si2.

Miodrag L. Kulic, "Interplay of Electron-Phonon Interaction and Strong Correlations: The Way to High-Tc Superconductivity." Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth, GERMANY; e-mail btp509@btp4x8.phy.uni-bayreuth.de.

Sergey V. Kuplevakhsky, "Exact Solution of the Lawrence-Doniach Model in Parallel Magnetic Fields." Department of Physics, Kharkov State University, 310077 Kharkov, UKRAINE; e-mail sergey.v.kuplevakhsky@univer.kharkov.ua; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9901218. 74.80.Dm; 74.20.De; 74.50.+r.

R. M. Langan, S. N. Gordeev, M. Oussena, P.A.J. de Groot, A.G.M. Jansen, R. Gagnon, and L. Taillefer, "Scaling Behavior of Magneto-Resistance in Clean YBa2Cu3O7-d Single Crystals in the Vortex Liquid State." To be published in Physica C (in press). Contact S. N. Gordeev, Department of Physics, University of Southampton, Southampton, SO17 1BJ, UNITED KINGDOM; telephone +44 1703 592958; telefax +44 1703 593910; e-mail sg@phys.soton.ac.uk. Key words: vortex liquid, vortex lattice melting, flux-flow resistance, multicritical point. 74.60.Ge; 74.72.Bk.

Urs Ledermann, Alban L. Fauchere, and Gianni Blatter, "Nonlocality in Mesoscopic Josephson Junctions with Strip Geometry." To be published in Phys. Rev. B. Theoretische Physik, Eidgenoessische Technische Hochschule, CH-8093 Zurich, SWITZERLAND; e-mail lederman@itp.phys.ethz.ch; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902134. 74.50.+r; 74.80.Fp.

Y. S. Lee, R. J. Birgeneau, M. A. Kastner, Y. Endoh, S. Wakimoto, K. Yamada, R. W. Erwin, S.-H. Lee, and G. Shirane, "Neutron Scattering Study of Spin Density Wave Order in the Superconducting State of Excess- Oxygen-Doped La2CuO4+y." Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139; e-mail younglee@yoko.mit.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902157. 74.72.Dn; 75.10.Jm; 75.30.Fv; 75.50.Ee; 75.70.Kw.

Yasukuni Matsumoto, Hideki Miyamoto, and Noriyuki Murata, "Characteristics of the Weibull Parameters Deduced from the I-V Curves Measured on the Sintered GdBa2Cu3O7-d." To be published in Advances in Supercond. XI: Proc. of the 11th Int. Symp. on Superconductivity (ISS'98), Fukuoka, Japan, Nov. 16-19, 1998; edited by N. Koshizuka and S. Tajima (Springer-Verlag, Tokyo). Department of Electrical Engineering, Fukuoka University, 8-19-1 Nanakuma, Jyonannku, Fukuoka 814-0080, JAPAN; telephone +81 92 871 6631, ext. 6344; telefax +81 92 871 7667; e-mail matumoto@tsat.fukuoka-u.ac.jp. Key words: I-V characteristics, Jc distribution, high-Tc superconductor, Weibull function.

I. I. Mazin and D. J. Singh, "Competitions in Layered Ruthenates: Ferro- vs. Antiferromagnetism and Triplet vs. Singlet Pairing." Code 6691, Naval Research Laboratory, Washington, DC 20375; e-mail mazin@dave.nrl.navy.mil; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902193.

D. Mihailovic and J. Demsar, "Time-Resolved Optical Studies of Quasiparticle Dynamics in High-Temperature Superconductors: Experiments and Theory." To be published in Application of Spectroscopy to Supercond. Mater., ACS Symp. Series, Vol. 730, edited by E. Faulques (ACS Publications, 1999). Solid State Physics Department, Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, SLOVENIA; J. Demsar's e-mail jure.demsar@ijs.si; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902243.

Grigorii P. Mikitik and Ernst Helmut Brandt, "Analytic Solution for the Critical State in Superconducting Elliptic Films." Contact Ernst Helmut Brandt, Max Planck Institut fuer Metallforschung, P.O. Box 800665, D- 70506 Stuttgart, GERMANY; telephone +49 711 689-1823; telefax +49 711 689-1010 or -1932; e-mail ehb@physix.mpi-stuttgart.mpg.de; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902186. 74.60.-w; 74.60.Ge.

Sharmila M. Mukhopadhyay, Roberto Garcia, and Niraj Mahadev, "Influence of Surface Doping on Sintering and Microstructure of a Superconducting Oxide." To be published in Physica C (in press). Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435; telephone (937) 775-5040; telefax (937) 775-5009; e-mail me_dept@cs.wright.edu. Key words: surface doping, sintering, superconducting oxide.

T. Niinae, Y. Ikeda, Y. Bando, M. Takano, Y. Kusano, and J. Takada, "Synthesis, Thermal Stability, Structural Features, and Electromagnetic Properties of Bi2+xSr2-xCuO6+d (0 <= x <= 0.4)." To be published in Physica C (in press). Contact M. Takano, Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011, JAPAN; telephone +81 774 383120; telefax +81 774 383125; e-mail takano@scl.kyoto-u.ac.jp. Key words: high-Tc superconductor, modulated structure, phase diagram, substitution effect.

H. Noji, "Calculation of ac Losses and Current Distributions in High-Tc Superconducting Layered Conductor." To be published in Physica C (in press). Interdisciplinary Research Centre in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UNITED KINGDOM; telephone +44 1223 33 7076; telefax +44 1223 33 7074; e-mail hn211@cam.ac.uk. Key words: ac loss, current distribution, superconducting conductor, electric circuit model. 74.25.Fy; 74.60.Jg; 74.72.Hs.

T. Ogawa, "Effect of the Cooling Time in YBa2Cu3O7-d Film Process on the Electrical Properties of Grain Boundary Josephson Junctions with the Tilt Angle of 24 degrees." To be published in Physica C (in press). Research Institute for Interface Quantum Electronics, Hokkaido University, North 13, West 8, Kita-ku, Sapporo 060-8628, JAPAN. Key words: grain boundary junctions, bicrystal, cooling time, Josephson characteristics.

M. P. Oomen, J. Rieger, M. Leghissa, B. ten Haken, and H.H.J. ten Kate, "Dynamic Resistance in a Slab-Like Superconductor with Jc(B) Dependence." Submitted to Supercond. Sci. & Technol. Siemens AG, ZT EN 4, Postfach 3220, D-91050 Erlangen, GERMANY; telephone +49 91317 34889; telefax +49 91317 33323; e-mail student2.zten4@erls.siemens.de. 74.25.Fy; 74.25.Ha.

Frank J. Owens, "Evidence of a Phase Transition in Cu-O Chains of LiCuO2." To be published in Physica C (in press). Energetic Materials Laboratory, Armament Research, Development and Engineering Center, Bldg. 3022, Picatinny, NJ 07806. Key words: phase transition, Cu-O chains, LiCuO2.

Catherine Pepin and Patrick A. Lee, "Exact Density of States in a System of Disordered Two Dimensional Dirac Fermions in the Unitarity Limit: The d-Wave Superconductor." Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139; e-mail at Oxford, UNITED KINGDOM c.pepin1@physics.ox.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9811328.

Frank Pfeiffer and Heiko Rieger, "Numerical Study of the Strongly Screened Vortex Glass Model in an External Field." Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Str. 77, D-50937 Koeln, GERMANY; Heiko Rieger's e-mail at Juelich h.rieger@fz-juelich.de; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902289.

G. G. Qian, K. Q. Ruan, X. H. Chen, C. Y. Wang, L. Z. Cao, and M. R. Ji, "The Electronic Structure and Transport Properties of Bi2Sr2-xLaxCaCu2Oy (x=0.0-0.8)." To be published in Physica C (in press). Structure Research Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, PEOPLE'S REPUBLIC OF CHINA; e-mail caolz@ustc.edu.cn. Key words: thermoelectric power, transport property, Bi2Sr2-xLaxCaCu2Oy.

Z. F. Ren, W. Li, D. Z. Wang, J. Y. Lao, J. H. Wang, M. Paranthaman, D. T. Verebelyi, D. K. Christen, D. F. Lee, A. Goyal, and D. M. Kroeger, "In-Plane Aligned Superconducting Tl0.78Bi0.22Sr1.6Ba0.4Ca2Cu3O9 Films on Rolling Assisted Biaxially Textured Substrates." To be published in Physica C (in press). Department of Physics, Center for Advanced Photonic and Electronic Materials (CAPEM), State University of New York at Buffalo, Buffalo, NY 14260-3000; telephone (716) 645-6800, ext. 2241; telefax (716) 645-6949; e-mail zren@acsu.buffalo.edu. Key words: laser ablation, temperature, anneal.

J. Roehler, C. Friedrich, T. Granzow, E. Kaldis, and G. Boettger, "Phase Separation in Overdoped Y1-0.8Ca0-0.2Ba2Cu3O6.96-6.98." To be published in High Temperature Superconductivity: AIP Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999, edited by S. E. Barnes. II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicherstr. 77, D-50937 Koeln, GERMANY; e-mail abb12@rs1.rrz.uni-koeln.de; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902030.

I. Sargankova, W. Koenig, M. Mair, G. Gritzner, J. Kovac, M. Reissner, and P. Diko, "Microstructure and Superconducting Characteristics of HgxPbyBa2Ca2Cu3O8+d." To be published in Studies of High Temp. Supercond., Vol. 27/28 -- Microstructural Studies in HTSC, edited by A. V. Narlikar (Nova Science Publishers, New York). Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04353 Kosice, SLOVAKIA.

Nick Savvides and Karl-Heinz Mueller, "ac Susceptibility of a Monofilament Bi-2223/Ag Superconducting Tape in a Perpendicular Field." To be published in Physica C. CSIRO Telecommunications and Industrial Physics, Bradfield Road, West Lindfield, P.O. Box 218, Lindfield NSW 2070, AUSTRALIA; telephone +61 2 9413 7359; telefax +61 2 9413 7202; e- mail nick.savvides@tip.csiro.au. Key words: superconductors, ac susceptibility, ac loss, eddy current loss. 85.25.Ly; 75.40.Cx; 75.40.Gb.

A. Serquis, F. Prado, and A. Caniero, "On the Role of the Reduction Step in Nd1.85Ce0.15Cu1+-dOy: A Study of Thermodynamic Properties and Electrical Resistivity at High Temperature." To be published in Physica C (in press). Contact A. Caneiro, Instituto Balseiro y Centro Atomico Bariloche, Comision Nacional de Energia Atomica, 8400 S.C. de Bariloche, ARGENTINA; telephone +54 944 45274; telefax +54 944 45299; e-mail caneiro@cab.cnea.edu.ar. Key words: electron-doped superconductor, defect structure, oxygen stoichiometry, electrical resistivity. 74.25.Bt; 74.25.Fy; 74.62.Bf; 74.62.Dh.

D. V. Shantsev, M. R. Koblischka, Y. M. Galperin, T. H. Johansen, L. Pust, and M. Jirsa, "Central Peak Position in Magnetization Loops of High-Tc Superconductors." Submitted to Phys. Rev. Lett. Department of Physics, University of Oslo, P.O. Box 1048, Blindern, N-0316 Oslo, NORWAY; Y. M. Galperin's e-mail iouri.galperine@fys.uio.no; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9812222. 74.25.Ha; 74.76.Bz; 74.80.Bj.

P. V. Shevchenko, V. N. Kotov, and O. P. Sushkov, "Spectrum of Elementary and Collective Excitations in the Dimerized S=1/2 Heisenberg Chain with Frustration." School of Physics, University of New South Wales, Sydney 2052, AUSTRALIA; e-mail pavel@newt.phys.unsw.edu.au; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9901302. 75.10.Jm; 75.30.Ds; 75.40.Gb.

Masaki Shigemori, Akira Shimizu, Tobias Brandes, and Jun-ichi Inoue, "Strong Enhancement of Superconducting Correlation in a Two-Component Fermion Gas." Submitted to J. Phys. Soc. Jpn. Department of Basic Science, School of Arts and Sciences, Tokyo University, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, JAPAN; e-mail shige@asone.c.u-tokyo.ac.jp; Web site http://as2.c.u-tokyo.ac/jp/~shige/; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902079.

M. Sigrist, D. Agterberg, A. Furusaki, C. Honerkamp, K. K. Ng, T. M. Rice, and M. E. Zhitomirsky, "Phenomenology of the Superconducting State in Sr2RuO4." To be published in Proc. of the First Crete Euroconference on Anomalous Complex Superconductors (ACS-1), Aghia Pelaghia, Crete, Greece, Sept. 25-Oct. 2, 1998. Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, JAPAN; A. Furusaki's e-mail furusaki@yukawa.kyoto-u.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902214.

T. Stein, G. A. Levin, C. C. Almasan, D. A. Gajewski, and M. B. Maple, "Quantum Creep in Y1-xPrxBa2Cu3O7-d Crystals: Magnetic Relaxation and Transport." Department of Physics, Kent State University, Kent, OH 44242; e-mail phyxs722@zeus.kent.edu; C. C. Almasan's e-mail calmasan@physics.kent.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902076.

H. Suematsu, M. Nagase, Y. Tomokiyo, M. Karppinen, and H. Yamauchi, "Application of Convergent-Beam-Electron-Diffraction Technique to Determine Novel Cuprate Structures." To be published in Advances in Supercond. XI: Proc. of the 11th Int. Symp. on Superconductivity (ISS'98), Fukuoka, Japan, Nov. 16-19, 1998; edited by N. Koshizuka and S. Tajima (Springer-Verlag, Tokyo). Contact H. Yamauchi, Materials & Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, JAPAN; telephone +81 45 924-5315; telefax +81 45 924-5365 or -5360; e-mail yamauchi@materia.titech.ac.jp. Key words: CBED technique, BaY(Cu0.5,Fe0.5)2O5+d, oxygen content, magnetic properties, space group determination.

F. Taddei, S. Sanvito, J. H. Jefferson, and C. J. Lambert, "Suppression of Giant Magnetoresistance by a Superconducting Contact." Submitted to Phys. Rev. Lett. School of Physics and Chemistry, Lancaster University, Lancaster LA1 4YB, UNITED KINGDOM; e-mail f.taddei@lancaster.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9901347. 74.80.Dm.

K. Tanaka and F. Marsiglio, "Even-Odd and Super-Even Effects in the Attractive Hubbard Model." Department of Physics, University of Alberta, Edmonton, Alberta, CANADA T6G 2J1; e-mail ktanaka@phys.ualberta.ca; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902173. 74.20.Fg; 71.24.+q; 71.10.Fd; 71.10.Li.

Alexander N. Ulyanov, "Transport of ac and dc Current by Hard Superconductors: Critical and Resistive State." To be published in J. Appl. Phys. Donetsk Physico-Technical Institute of National Academy of Sciences of Ukraine, St. R. Luxemburg 72, 340114 Donetsk-114, UKRAINE; e-mail ulyanov@host.dipt.donetsk.ua.

G. Villard, A. Daignere, D. Pelloquin, and A. Maignan, "Effect of Underdoping on the Superconductivity of (Hg,Cu)Ba2CuO4+d '1201' Single Crystals." To be published in Physica C. Laboratoire CRISMAT, UMR 6508 associee au CNRS, ISMRA et Universite de Caen, 6 Boulevard du Marechal Juin, F-14050 Caen Cedex, FRANCE.

J.Y.T. Wei, N.-C. Yeh, C. C. Fu, and R. P. Vasquez, "Tunneling Spectroscopy Study of Spin-Polarized Quasiparticle Injection Effects in Cuprate/Manganite Heterostructures." To be published in J. Appl. Phys. Department of Physics, California Institute of Technology, Pasadena, CA 91125.

Z. Y. Weng, "Why Tc is Too High When Antiferromagnetism is Underestimated? An Understanding Based on the Phase-String Effect." Presented at University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. 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 or zyweng@uh.edu; preprint also available at http://xxx.lanl.gov/abs/cond- mat/9902124.

X. S. Wu and J. Gao, "Structure and Transport Properties in Calcium- Doped YBa1.8Nd0.2Cu3Oy Cuprates." To be published in Physica C (in press). National Laboratory of Solid State Microstructures, Department of Physics, Institute of Solid State Physics, Nanjing University, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA; telefax +86 25 3300 535; e- mail xswu@netra.nju.edu.cn. Key words: YBa1.8Nd0.2Cu3Oy with Ca doping, transport properties, superconductivity, structure.

X. S. Wu and J. Gao, "Superconductivity and Structural Changes in Y0.8Ca0.2Ba2-xNdxCu3Oy Cuprates with x <= 0.50." To be published in Physica C (in press). National Laboratory of Solid State Microstructures, Department of Physics, Institute of Solid State Physics, Nanjing University, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA; telefax +86 25 3300 535; e-mail xswu@netra.nju.edu.cn. Key words: Y0.8Ca0.2Ba2Cu3Oy with Nd doping, superconductivity, structure.

Y. Yajima, T. Manabe, I. Yamaguchi, T. Shimizu, S. Mizuta, and T. Kumagai, "Sr-Substitution Limit at 760-800^oC in Epitaxial Yb(Ba1- xSrx)2Cu4O8 Films Prepared by Coating-Pyrolysis Process." To be published in Physica C (in press). Chiba Institute of Technology, Narashino 2-17-1, Chiba 275-0016, JAPAN; telephone +81 298 54-4556; telefax +81 298 54-4709 or -4487; e-mail yu-ichi@muc.biglobe.ne.jp; preprint also available from T. Manabe, National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305-8565, JAPAN; e-mail manabe@home.nimc.go.jp. Key words: Yb(Ba1-xSrx)2Cu4O8, thin film, epitaxy, substitution limit, c-axis length, Tc. 74.25.Dw; 81.15.Np; 74.62.Dh; 74.76.-w.

N.-C. Yeh, R. P. Vasquez, C. C. Fu, A. V. Samoilov, Y. Li, and K. Vakili, "Non-Equilibrium Superconductivity Under Spin-Polarized Quasiparticle Currents in Perovskite Ferromagnet-Insulator- Superconductor (F-I-S) Heterostructures." Submitted to Phys. Rev. Lett. Department of Physics, California Institute of Technology, Pasadena, CA 91125. 74.80.Dm; 74.50.+r; 74.60.Jg.

Oron Zachar, "Effect of Magnetic Field on Overdoped HTc Superconductors: Conflicting Predictions of Various HTc Theories." Laboratoire de Physique des Solides, Universite de Paris-Sud, F-91405 Orsay Cedex, FRANCE; e-mail zachar@lps.u-psud.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902130.

Th. Zahner, R. Stierstorfer, S. Reindl, T. Schauer, A. Penzkofer, and H. Lengfellner, "Picosecond Thermoelectric Response of Thin YBa2Cu3O7-d Films." To be published in Physica C (in press). Contact H. Lengfellner, Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitatstrasse 31, D-93040 Regensburg, GERMANY; telephone +49 941 943 2075; telefax +49 941 943 4223; e-mail hans.lengfellner@physik.uni-regensburg.de. Key words: picosecond thermoelectric response, YBa2Cu3O7-d films, transverse Seebeck effect.

A. J. Zaleski and J. Klamut, "The Influence of Ni and Zn Substitution on Anisotropy of the Penetration Depth in La1.85Sr0.15CuO4." To be published in Phys. Rev. B. Institute for Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw, POLAND; telephone +48 71 343 50-21 to -29; telefax +48 71 441 029; e- mail zaleski@int.pan.wroc.pl. 74.25.Ha; 74.62.Dh; 74.72.Dn.

COMING EVENTS (An * indicates a previously listed event. Also see complete listing of upcoming conferences and workshops at our Web site http://www.iitap.iastate.edu/htcu/comevents.html.)

April 25 - 28, 1999: 5th Twente Workshop: Digital Applications, Josephson Junctions and Sensors, University of Twente, Enschede, The Netherlands. Aim is an international exchange of latest results on the electronic applications of superconductors. The workshop should yield an extended review on the following areas of research: digital applications, RSFQ-logic, sensors, film growth, Josephson junctions, and interconnects. Morning sessions will be devoted to invited talks with discussion breaks; afternoon sessions will consist of presentations of contributed papers. Opportunities will be offered for a daily poster session to stimulate discussions. Abstract deadline, March 15, 1999, (preferably by e-mail). Papers will be published as a special issue of Physica C. Contact Ir. H.J.H. Smilde, University of Twente, Department of Applied Physics, (TN/LT), P.O. Box 217, 7500 AE Enschede, The Netherlands; telephone +31 53 489 3841; telefax +31 53 489 1099; e-mail h.j.h.smilde@tn.utwente.nl.

May 31 - Aug. 27, 1999: Topological Defects in Non-Equilibrium Systems and Condensed Matter Seminar, Max-Planck-Institut Fuer Physik Komplexer Systeme, Dresden, Germany. In conjunction with the International Workshop on Computer-Aided Analysis of Dynamical Structures and Defects (July 20 - 29, 1999). Aim is to bring together scientists from the non- equilibrium physics community with those in equilibrium condensed-matter physics community, to discuss methods and tools of studies of dynamics of disordered media dominated by formation, motion, and annihilation of topological defects. The applications include nonequilibrium patterns in fluid mechanical, chemical, and nonlinear optical systems, as well as dynamics of superfluids, superconductors, liquid crystals, and other ordered media. Scope may range from understanding the appearance, structure, and dynamics of weakly disordered states to elucidating the role of different forms of vorticity in various strongly turbulent states, and understanding different forms of frozen disorder ("vortex glass") and relation between topological defects and other localized structures. For further information and application forms, contact Visitors Program, Max-Planck-Institut fuer Physik Komplexer Systeme, Noethnitzer Str. 38, D-01187 Dresden, Germany; telephone +49 351 871 2105; telefax +49 351 871 2199; e-mail canla@mpipks-dresden.mpg.de; Web site http://www.mpipks-dresden.mpg.de/~canla/index.html.

Aug. 1 - 3, 1999: Symposium on Micro- and Nanocryogenics (MNC), University of Jyvaskyla, Jyvaskyla, Finland. Satellite to the LT-22 Conference in Helsinki, Finland (Aug. 4-11, 1999). Will focus on the growing field of cryogenic applications of micro- and nanometer size systems. Topics of the symposium include: microrefrigeration, thermometry, microbolometers and other space applications, SQUIDs and their applications, and other cryogenic applications of micro- and nanostructures. Abstract deadline, March 31, 1999. Limited to about 100 persons. For further information, contact Minna Ranta (MNC), Department of Physics, University of Jyvaskyla, P.O. Box 35 (Y5), FIN- 40351 Jyvaskyla, Finland; telephone +358 14 602354; telefax +358 14 602351; e-mail mnc@phys.jyu.fi. Or contact Jukka Pekola (Conference Chair) at ukka.Pekola@phys.jyu.fi, or Antti Manninen (Co-Chair) at Antti.Manninen@phys.jyu.fi. Also see the MNC Web page at http://www.phys.jyu.fi/jyflweb/latest/mnc.html.

Nov. 2 - 4, 1999: The Third International Workshop on Material Science (IWOMS'99), Hanoi, Vietnam. Workshop covers various aspects of materials science, from bulk to nanoscale materials, including fundamentals and technical applications. Main objective is to provide a forum where most relevant and recent results are discussed. Topics include: intermetallics -- phase diagram, microstructure, and physical properties; magnetic materials and applications; thin films -- materials and applications; high-Tc superconductors and superconductivity-related phenomena; advanced ceramic materials; physics of nanostructures; and others. Invited and contributed papers. Workshop language is English. Abstract deadline, April 15, 1999. For information, contact Secretary IWOMS'99, International Training Institute for Materials, Science (ITIMS), ITIMS Building, Dai hoc Bach Khoa Hanoi, 1 DAI CO VIET Road, Hanoi, Vietnam; telephone +84 4-869-2518 or -868-0787; telefax +84 4- 869-2963; e-mail iwoms@itims.edu.vn.

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

Position open: A postdoctoral position is available at the University of Maryland to run scanning near-field microwave-microscopy program. Work funded by NSF Materials Research Science and Engineering Center on Oxide Thin Films. Primary responsibility is to supervise three graduate students and develop new quantitative imaging techniques of ferroelectric, ferromagnetic, and superconducting oxide materials. Goals are to develop quantitative images of electric polarization, ferromagnetic domains, and superconducting nonlinearities, all on sub- micron length scales and at microwave frequencies. A secondary objective is to contribute to another NSF-funded program to image microwave electromagnetic fields from cryogenic devices. The candidate should be familiar with microwave-measurement techniques and have an interest in the physics and materials properties of novel oxide materials. For information, contact Prof. Steven Anlage, Physics Department, University of Maryland, College Park, MD 20742-4111; telephone (301) 405-7321; telefax (301) 405-3779; e-mail anlage@squid.umd.edu; Web site http://www.csr.umd.edu.

Research positions open: The following positions are available for PhD students and postdoctoral fellows at the Condensed Matter Physics Department of the Vrije Universiteit.

Position 1: Complex Oxide Films -- Growth and Physical Properties -- The target of this activity is to synthesize hetero-epitaxial complex oxides such as bismuth-doped garnets, superconducting compounds, and magnetoelectric films and to study their physical properties. In general, the main aim of this material-science activity is to unravel the fascinating links between physical properties, defect structure, and growth conditions of complex oxides.

Position 2: Vortex Dynamics in Superconductors -- Vortex matter in high-Tc superconductors is investigated by means of high-resolution torque magnetometers and magneto-optics. Setup is especially well- suited to study roughening and growth of flux penetration in films which exhibit essentially the same characteristics as burning paper! Vortex matter is thus an attractive model system to study nonlinear diffusion phenomena.

Applicants should have obtained recently a M.Sc. degree (for PhD student positions) or a PhD degree (for postdoc positions) in experimental physics, physical chemistry, or materials science. They should have an excellent knowledge of condensed-matter physics. The PhD-student positions are for four years and the postdoctoal positions for two years.

Candidates should send a curriculum vitae and the names of three references to Prof. R. Griessen, Faculty of Sciences, Division of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; telephone +31 20 4447915; e-mail griessen@nat.vu.nl; Web site http://www.nat.vu.nl/vakgroepen/vstof/english/tmr/index.html.

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. 13, #6, March 15, 1999.