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MOCVD YBCO on IBAD YSZ
As reported by V. Selvamanickam (IGC) et al., a metal-organic-chemical- vapor-deposition (MOCVD) method has been developed to achieve high currents in YBa2Cu3O7-d (YBCO) superconducting films deposited on biaxially textured buffer layers over untextured metal substrates. Biaxially textured buffer layers of yttria-stabilized zirconia (YSZ), typically 0.5-1 micrometer thick, were deposited on polished Hastelloy-C and Inconel 625 metal substrates (thickness ~~ 100 micrometers) by ion- beam-assisted deposition (IBAD). To deposit the YBCO films on the YSZ, tetramethyl heptanedionate (THD) precursors for Y, Ba, and Cu were vaporized, the vapors were mixed with a carrier gas of Ar and O2, and the precursor mixture was then injected into the MOCVD reactor, where YBCO films of thickness 1 micrometer were deposited within a temperature regime of 700-800^oC at a reactor pressure of 1-5 torr.
The IBAD YSZ buffer layers exhibited strong biaxial texture; the in- plane texture was 15-25 degrees full width at half maximum (FWHM). The YBCO films deposited on the YSZ-buffered metal substrates had the structure of a dense, continuous film with hardly any porosity but with numerous particulates, which were rich in Y. Despite the particulate formation, the YBCO films exhibited strong c-axis texture and good in- plane texture: ~~4 degrees FWHM.
Current-voltage (I-V) measurements were carried out with continuous dc currents up to 80 A on samples of thickness 1 micrometer and length 10 mm across the entire width of the film (3.5 mm) without any patterning. The authors report critical currents I_c and critical current densities Jc at 75 K (the boiling point of liquid N2 in Los Alamos) and at 64 K (obtained by pumping on the liquid N2). In self-field at 75 K, an I_c = 45 A was achieved, which corresponds to Jc = 1.3 x 10^6 A/cm^2. The dependence of Jc on magnetic field was examined with the field oriented parallel and perpendicular to the c axis. The dependence of Jc upon the angle theta between the magnetic field and the c axis also was measured for fields of 1, 2, 3, 4, 5, and 6 T. The magnetic-field dependence of Jc indicates a strong-linked behavior at low fields and strong pinning at high magnetic fields. The value of Jc increased by about a factor of three when the temperature was lowered from 75 to 64 K. The dependence of Jc on theta showed a peak due to intrinsic pinning when B was parallel to the layers (B (perp.) c, theta = 90 degrees) and no peak when B was perpendicular to the layers (B || c, theta = 0 degree).
Some representative reported values of Jc(B,theta,T) are Jc(1 T, 90 degrees, 75 K) = 5.7 x 10^5 A/cm^2, Jc(5 T, 90 degrees, 75 K) = 2.4 x 10^5 A/cm^2, Jc(1 T, 0 degree, 75 K) = 2.2 x 10^5 A/cm^2, Jc(2.5 T, 0 degree, 75 K) = 1.0 x 10^5 A/cm^2, Jc(2 T, 90 degrees, 64 K) = 1.2 x 10^6 A/cm^2, Jc(5 T, 90 degrees, 64 K) = 7.7 x 10^5 A/cm^2, Jc(1 T, 0 degree, 64 K) = 6.8 x 10^5 A/cm^2, Jc(2 T, 0 degree, 64 K) = 5.2 x 10^5 A/cm^2, Jc(5 T, 0 degree, 64 K) = 3.0 x 10^5 A/cm^2. The authors note that the high-current films still show numerous particulates, the reduction of which could lead to even higher current densities in YBCO films deposited by MOCVD. The authors also stress that this demonstration of high Jc, as well as high currents (I_c), in useful magnetic fields at 64 K and 75 K supports the viability of the MOCVD process as a candidate for the fabrication of YBCO coated conductors for electric power applications.
Films
A preprint by M. Lorenz (Leipzig) et al. reports that a large-area pulsed-laser-deposition (PLD) process for high-quality YBCO thin films on both sides of R-plane sapphire substrates with CeO2 buffer layers is being used routinely to optimize planar microwave filters for satellite and mobile communication systems. With the experience of more than 700 double-sided three-inch-diameter YBCO:Ag films, the authors have achieved a high degree of reproducibility of Jc values above 3.5 x 10^6 A/cm^2 and state-of-the-art R_s values. A high degree of reproducibility and uniformity is revealed in maps (2D scans) of the critical current density Jc and microwave surface resistance R_s across the wafers. The authors also discuss the potential of YBCO/SrTiO3/YBCO/CeO2 film systems on R-plane sapphire wafers for use in tunable microwave resonators.
The electrical properties of 10 degree-tilted YBCO films grown epitaxially upon as-received (106) SrTiO3 substrates are described in a preprint by P. S. Czerwinka (Nottingham) et al. The authors report that the normal and superconducting properties exhibit significant differences depending upon whether the YBCO films are grown upon unannealed or annealed substrates.
High-Tc bilayers and trilayers based on NdBa2Cu3O7-d (NBCO) using Sr2AlTaO6 (SAT), Sr2AlNbO6 (SAN), and lanthanum-doped SAT [LaxSr2- xAlTaO6 (LSAT)] as insulators have been grown in-situ on SrTiO3 substrates by Y. Li et al. (SRL-ISTEC) using PLD. The high stability and compatibility with sharp interfaces of these multilayers were demonstrated by TEM observations. Although the as-grown bilayers showed a low Tc value of ~50 K, the top and bottom NBCO layers showed a Tc of 87-90 K and Jc > 1 x 10^6 A/cm^2 at 77 K after annealing in O2 at 450^oC.
The characteristics of NBCO Josephson junctions fabricated by the high- resolution focused-ion-beam (FIB) etching technique have been investigated by K. Ohnishi et al. (SRL-ISTEC). After optimization of the FIB etching technique, the junctions exhibited RSJ-like characteristics. The spreads in I_c and R_n for 29 working junctions on the same substrate at 4.2 K were 40% and 60%, respectively. The I_c spread was caused primarily by the instability of the FIB and the substrate temperature during thin-film deposition.
Applications
The development of YBCO, low-noise, direct-coupled high-Tc superconducting-quantum-interference-device (SQUID) magnetometers based on 30 degrees bicrystal junctions is reported by F. Ludwig and D. Drung (PTB-Berlin). These magnetometers consist of a 100 pH SQUID loop with a linewidth of 4 micrometers and a pickup coil consisting of 16 parallel 50-micrometer-wide loops. The magnetic-field noise down to 1 Hz did not increase when the magnetometers were exposed to ac fields with peak-to- peak amplitudes of up to 54 micro-Tesla or cooled in static magnetic fields above that of the earth. The lowest noise at 1 Hz of such a device cooled in 64 micro-Tesla was 65 fT Hz^[1/2]. The increased noise below 1 Hz when the devices were cooled in a static magnetic field can be quantitatively described by the measured temperature fluctuations assuming a temperature coefficient of the pickup loop area of about 1 x 10^[-4]/K.
RBa2Cu3O7-d
Measurements of the nonresonant microwave absorption in a YBa2Cu3O7-d (YBCO or Y-123) bulk sample have been carried out by J. Yamada et al. (Mie) as a function of the dc field sweep rate at 77 K. The authors found that the absorption increases with increasing sweep rate and that it saturates at the highest sweep rates. The authors interpret this behavior in terms of different flux profiles near the surface at different sweep rates.
Levitation and stability forces have been studied by W. Hennig et al. (TCSUH) using YBCO trapped-field magnets (TFMs) to replace permanent magnets (PM). TFMs with maximum trapped field B_[TFM] up to 1.6 T at 77 K were used and compared with a PM with B_[PM]= 0.34 T at its surface. The authors found that the levitation force with the TFM can be more than a factor of 10 larger than that with the PM. The authors also found that both levitation and stability forces can be significantly increased using multi-sample systems.
As reported by W. Lo et al. (IRC-Cambridge), large, single-grain NdBa2Cu3O7-d (NBCO or Nd-123) composites containing Nd4Ba2Cu2O10 (Nd- 422) phase inclusions have been fabricated up to 2 cm in diameter using a top-seeded melt-textured-growth technique. An MgO single-crystal seed was used to provide a heterogeneous nucleation site at the center of a pre-sintered pellet, which was heated above its peritectic temperature and then cooled continuously in a conventional tube furnace in reduced oxygen partial pressure. For magnetic fields applied both perpendicular and parallel to the crystallographic c axis, the NBCO grains exhibited a very high irreversibility field (> 9 T at 77 K), which is significantly higher than that observed in good-quality melt-processed YBCO.
Transport and magnetic-relaxation properties of the mixed state in strongly underdoped Y1-xPrxBa2Cu3O7-d single crystals have been studied by T. Stein (Kent State) et al. using a flux-transformer contact configuration. The authors observed two correlated phenomena: a coupling transition and a transition to quantum creep. The distribution of transport current below the coupling transition was found to be highly nonuniform, which facilitates quantum creep. The authors speculate that in the mixed state below the coupling transition, where dissipation is nonohmic, the current distribution may be unstable with respect to self-channeling, resulting in the formation of very thin current-carrying layers.
Strong signatures of Mg substitution in YBa2(Cu1-xMgx)3O7-d have been obtained by J. Figueras et al. (Bellaterra) from single-domain samples prepared by top-seeding using YBa2Cu3O7-d + 30 wt% Y2BaCuO5 + X wt% MgO mixtures. The authors found a drastic decrease of the superconducting transition temperature with increasing X, reaching Tc ~ 40 K for X = 16.7. The Tc(x) dependence and thermogravimetric results suggest that Mg atoms substitute for Cu on Cu(2) sites and that a solubility limit exists.
Bi Cuprates
The temperature dependence of electronic Raman scattering has been explored by O. V. Misochko (Chernogolovka and KARC) in Bi2Sr2CaCu2O8+d (Bi-2212) crystals. In optimally doped crystals, the temperature dependence of the static Raman (omega --> 0) slope suggests that the gap nodes are shifted from the positions they would have for pure d-wave pairing. The author also notes that the low-frequency part of the B_[1g] spectra as a function of progressively stronger disorder gives further evidence for a mixed order parameter.
A preprint by V. M. Krasnov (Chernogolovka) et al. reports a study and comparison of the perpendicular (c-axis) transport properties of the layered high-Tc superconductor (HTS) Bi-2212 and low-Tc (LTS) Nb/Cu multilayers. For both HTS and LTS samples, similar anomalous features were observed: (a) The c-axis critical current I_c is multiple-valued as a function of temperature T and in-plane magnetic field H. (b) I_c exhibits extremely large fluctuations, and the probability distribution P(I_c) has multiple maxima. (c) The I_c(H) patterns are aperiodic. (d) In the dynamic state, the flux-flow branches in current-voltage characteristics consist of multiple closely spaced sub-branches and exhibit large fluctuations due to switching between sub-branches. The experimental data are in qualitative agreement with numerical simulations for a stack of long, strongly coupled Josephson junctions. All this is taken as evidence for the existence of multiple quasiequilibrium Josephson fluxon modes in these samples.
The subsolidus equilibria and the primary phase field (crystallization field) of the 110 K high-Tc (Bi,Pb)2Sr2Ca2Cu3O10+d [(Bi,Pb)-2223] phase in the presence of Ag under an atmosphere of 7.5 vol% O2 + 92.5 vol% Ar have been determined by W. Wong-Ng (NIST-Gaithersburg) et al. The authors studied a total of 29 six-phase volumes that include both the (Bi,Pb)-2223 and Ag phases. These subsolidus volumes were similar to those observed without the presence of Ag. The compositional ranges of initial melts of these volumes on a mole fraction basis were 5.6-25.3% BiO1.5, 0.4-13.8% PbO, 8.4-31.9% SrO, 12.2-33.3% CaO, 21.7-40.9% CuO, and 1.2-6.3% AgO0.5. From the data, the authors constructed the primary crystallization field for the (Bi,Pb)-2223 phase in the presence of Ag using the convex hull technique. A section through this "volume" portrayed by holding the AgO0.5, SrO, and CaO components at the median value of the 29 compositions while allowing projection on the other three axes (BiO1.5, PbO, and CuO). The net effect of Ag on the melt composition is a reduction in the PbO concentration and an increase in the SrO content.
The melting equilibria of Bi1.8Pb0.4Sr2Ca2.2Cu3O10+d under oxygen have been determined by W. Wong-Ng and L. P. Cook (NIST-Gaithersburg).
The effects of bend strains on monocore Bi-2223 tapes have been studied by N. Vasanthamohan et al. (Argonne) using transport measurements, magneto-optical imaging, and electron microscopy. The authors find that the observed strain tolerance is largely determined by the interplay of nonuniform strains and microstructural variation across the tape cross section, leading to nonuniform I_c values. The authors find that a model accounting for the observed concentration of the critical current density at the Ag/Bi-2223 interface can provide an explanation for the measured strain dependence on the retained I_c.
The effect of bending cycles on Ag/Bi-2223 composites in the form of tapes with 1, 7, and 19 ceramic filaments has been studied by M. T. Malachevsky and D. A. Esparza (Bariloche). The authors found that multifilamentary tapes better withstand cycling.
Other Cuprates
As discussed by Z. A. Xu (Princeton) et al., the Nd-doped cuprate La2-y- xNdySrxCuO4 displays a first-order phase transition at T_d (= 74 K for x = 0.10, y = 0.60) to a low-temperature tetragonal (LTT) phase. A magnetic field H applied parallel to the a axis leads to an increase in T_d, but when H is parallel to c, T_d is decreased. These effects show that magnetic ordering involving both Nd and Cu spins plays a key role in driving the LTO-LTT transition. The authors also observed related anisotropic effects in the uniform susceptibility and the in-plane magnetoresistance.
A preprint by E. Kandyel et al. (SRL-ISTEC) reports the synthesis of (La1-xSrx)8Cu8O20-d (8-8-20 phase) compounds with x in the range 0.25 <= x <= 0.65 using an O2 HIP apparatus. The electrical resistivity and magnetic susceptibility showed metallic behavior from room temperature down to 5 K with no sign of superconductivity.
A double-TlO-layer superconductor with three CuO2 sheets in the Tl-Sr- Ca-Cu-O system, (Tl1-xHgx)2Sr2Ca2Cu3Oy [(Tl,Hg)-2223, x = 0.35], has been synthesized by E. Kandyel et al. (SRL-ISTEC) using a high-pressure, high-temperature technique. As-prepared samples exhibited superconductivity below 103 K. The authors also synthesized (Tl1- xHgx)2Sr2CaCu2Oy [(Tl,Hg)-2212, x = 0.35] under 3 GPa. It showed a superconducting transition at 60 K, which is 35 K higher than that reported for samples synthesized under ambient pressure.
The electronic Raman spectra of strongly underdoped HgBa2Ca2Cu3O8+d (Hg- 1223) have been studied by A. Sacuto (Ecole Normale Superieure) et al. The authors were able to report with good accuracy the pure electronic Raman scattering (without subtraction of phonons) in the B_[2g], B_[1g], A_[1g] + B_[2g], and A_[1g] + B_[1g] channels. The d_[x^2-y^2] model fits the low-energy part (below 350 cm^[-1]) of the spectra for B_[2g] and A_[1g] symmetries and up to the gap energy for B_[1g]. However, to reconcile the upper part of the B_[1g] and B_[2g] spectra (above 350 cm^[-1]) with the d_[x^2-y^2] model, the authors needed to expand the B_[2g] vertex to the next order of Fermi-surface harmonics. The sharp and intense maximum in mixed A_[1g] symmetries is not easy to interpret in the framework of the d_[x^2-y^2] model.
After analyzing tunneling, inelastic neutron scattering, and torque measurements in a variety of hole-doped high-Tc cuprates, A. Mourachkine (Brussels) concludes that the Cooper pairs in the cuprates consist of spinons and that the pairing order parameter has anisotropic s-wave symmetry, whereas the order parameter for long-range phase coherence has a magnetic origin due to spin fluctuations and has d_[x^2-y^2] symmetry.
Vortices
The main features of Hall tunneling of pancake vortices in superclean high-Tc superconductors have been considered theoretically by D. A. Gorokhov and G. Blatter (ETH-Zurich). The authors describe the general formalism for the calculation of the lifetime of a vortex pinned in a metastable configuration. The authors apply their results to the problem of quantum tunneling of a pancake vortex from a columnar defect in the limit of a small driving current.
Pancake vortices in stacks of thin superconducting films or layers have been considered by R. G. Mints (Tel Aviv) et al. The authors find that in the absence of Josephson coupling, topological restrictions upon possible configurations of vortices are removed, and various structures forbidden in bulk superconductors can occur. In particular, the authors show that vortices may skip surface layers in samples of less than a certain size R_c, which might be macroscopic. Josephson coupling suppresses the R_c estimates.
At T << Tc, the flux-flow voltage in the cuprate superconductor Nd2- xCexCuO4 shows an intrinsic step structure, also leading to negative differential resistivity. R. P. Huebener (Tuebingen) et al. explain this in terms of subbands between the Fermi energy and the gap energy affecting the quasiparticle dynamics. In the presence of the electric field generated by current-induced vortex motion, the quasiparticle energy can be shifted to the upper band edge, resulting in Bragg reflection and Bloch oscillations. The subbands originate from the Andreev bound states in the vortex core via the interaction between vortices.
Local ac screening measurements in YBCO single crystals with twin boundaries have been carried out by G. A. Jorge and E. Rodriguez (Buenos Aires). For applied fields along the c direction, the authors found that at high temperatures, the twin boundaries serve as barriers to flux motion and thus enhance vortex pinning. At low temperatures, however, the twin boundaries act as channels for easy vortex motion.
The angular dependence of the in-plane resistivity rho(T,H,theta) of melt-textured YBa2Cu3O7-d/Y2BaCuO5 composites has been measured by T. Puig (Barcelona) et al. over a wide range of magnetic fields and temperatures. From the results, the authors identify a new region in the vortex-liquid state where twin-boundary pinning defines a partially entangled liquid vortex state characterized by short-range c-axis vortex coherence.
Three preprints by Yu. A. Genenko (Goettingen and Donetsk) et al. report calculations of the current-density and magnetic-flux distributions in a superconducting strip surrounded by soft magnetic material with a high magnetic permeability. The authors show that the current-density distribution is strongly affected by the shape of the magnetic surroundings. Depending upon the geometry, this effect may either suppress the total transport critical current of the strip or else enhance it up to magnitudes much larger than the critical current of the isolated strip.
A preprint by M.A.R. LeBlanc (Ottawa) et al. reports on measurements of
the evolution of the magnetization
A preprint by A. A. Zhukov (Southampton and Moscow State) et al. reports
the observation of a negative dynamic creep rate, i.e., increasing
irreversibility in the magnetic hysteresis loop for decreasing sweep
rate of the magnetic field, in both YBa2Cu3O7-d and 2H-NbSe2 single
crystals. This phenomenon was found to appear on the increasing branch
of the peak effect, which corresponds to a state that is intermediate
between the dislocation-free Bragg glass and a highly disordered vortex
phase. The authors show that the origin of the anomalous creep is
connected to a negative differential resistance resulting from the N-
like shape of the current-voltage characteristics.
Measurements in the peak-effect regime in a single crystal of Ca3Rh4Sn13
have been carried out by S. Sarkar (TIFR-Mumbai) et al. using ac
susceptibility and dc magnetization. Two discontinuous first-order-like
transitions were found to occur, one near the onset of the peak effect
and the other near the peak position. The authors attribute this to a
stepwise fracturing or amorphization of the vortex lattice.
Theory
The quasiparticle resonant states around a single nonmagnetic impurity
with unitary scattering in a d-wave superconductor have been studied by
J.-X. Zhu (TCSUH) et al., who solved the Bogoliubov-de Gennes equations
based on a t-J model. The authors investigated both the spatial
variation of the order parameter and the local density of states (LDOS)
around the impurity. The authors found that: (a) A particle-hole-
symmetric system has a single symmetric zero-energy peak in the LDOS
regardless of the size of the superconducting coherence length xi_0.
(b) For the particle-hole-asymmetric case, an asymmetric splitting of
the zero-energy peak is intrinsic to a system with a small value of
k_Fxi_0, in qualitative agreement with the experimental results of A.
Yazdani et al., Phys. Rev. Lett. 83, 176 (1999).
Using a path-integral formulation, Q.-H. Wang (Nanjing) and Z. D. Wang
(Hong Kong) have derived microscopically a Ginzburg-Landau free energy
with Zeeman coupling between the magnetic field and the orbital angular
momentum of the Cooper pairs in a superconductor with singlet pairing in
the dominant d_[x^2-y^2] and subdominant d_[xy] channels. With Zeeman
coupling and the Doppler energy shift due to the moving superfluid for
quasiparticle excitations, the authors arrive at a coherent
interpretation of two recent experiments on the thermal conductivity in
Bi-2212 [K. Krishana et al., Science 277, 83 (1997), and H. Aubin et
al., Phys. Rev. Lett. 82, 624 (1999)].
Functional-integral techniques have been used by J. P. Wallington and J.
F. Annett (Bristol) to examine the nearest-neighbor attractive Hubbard
model on a quasi-2D lattice. This is a simple phenomenological model
for the high-Tc cuprates that allows both extended (nonlocal) s- and d-
wave singlet superconductivity and mixed-symmetry states. Including
Gaussian fluctuations, the authors examine the crossover from weak-
coupling BCS superconductivity to the strong-coupling Bose-Einstein
condensation of composite s- or d-wave bosons, and they comment on the
origin and symmetry of the pseudogap.
Using numerical diagonalization of a 4 x 4 cluster, L. Arrachea (Buenos
Aires) and A. A. Aligia (Bariloche) have calculated on-site s, extended
s, and d_[x^2-y^2] pairing correlation functions (PCF) in an effective
generalized Hubbard model for the cuprates, with nearest-neighbor
correlated hopping and next-nearest-neighbor hopping t'. The authors
find that the vertex corrections to the PCF are significantly enhanced
relative to the t-t'-U model. The behavior of the PCF and their vertex
corrections, as well as signatures of anomalous flux quantization,
indicate superconductivity in the d-wave channel for moderate doping and
in the s-wave channel for high doping and small U.
The extended one-dimensional Hubbard model with attractive on-site
interaction U and nearest-neighbor repulsion V has been considered by A.
A. Aligia (Bariloche). The author constructs an effective Hamiltonian
H_[eff] for hopping t << V and arbitrary U < 0. Retaining the most
important terms, the author finds that H_[eff] can be mapped onto two
XXZ models, solved by the Bethe Ansatz. The quantum phase diagram shows
two Luttinger-liquid phases and a region of phase separation between
them. For some parameters, the results are in qualitative agreement
with experiments in Ba1-xKxBiO3.
A scheme for investigating the quantum dynamics of interacting electron
models by means of a time-dependent variational principle and spin-
coherent states of space lattice operators is proposed in a preprint by
A. Montorsi and V. Penna (Torino). The authors apply this scheme to the
one-dimensional Hubbard model, and they solve the resulting equations in
different regimes. In particular, they find that at low densities the
dynamics is mapped into two coupled nonlinear Schroedinger equations,
whereas near half filling the model is described by two coupled
Josephson-junction arrays.
A preprint by Y. Hasegawa (Himeji Institute of Technology) et al.
selects a number of possible odd-parity states group theoretically and
examines these in light of recent experiments on Sr2RuO4. The most
plausible candidates are time-reversal-symmetry broken states with line
nodes running either vertically or horizontally, consistent with
experiments. The authors propose experiments to distinguish between
these states.
Overviews
A book chapter on Raman scattering in high-Tc superconductors has been
prepared by M. Cardona (MPI-Stuttgart). The author notes that the
cuprates can be used to illustrate many techniques and applications of
Raman spectroscopy. In this chapter, the author reviews the theory and
the main experimental results concerning Raman light scattering by
phonons, electrons, and magnons in the high-Tc superconductors and
related materials (182 refs.).
An introduction to the electronic structure of high-Tc superconductors
is given in a review by J. Fink et al. (Dresden). The authors discuss
recent studies of model compounds containing copper-oxide planes,
ladders, and chains, performed using high-energy spectroscopies such as
photoemission, x-ray absorption, and electron energy-loss spectroscopy
(48 refs.).
Some insights regarding the path to higher Tc in cuprate superconductors
are given in a preprint by J. D. Jorgensen (Argonne): (1) For a given
compound, the maximum Tc is achieved by using a chemical variable to
optimize the carrier concentration. (2) When different compounds are
compared at their optimum doping, the highest Tc is observed for
compounds with flat CuO2 planes. (3) Tc also can be enhanced if the
charge reservoir region (blocking layer) is metallic. The author notes,
however, that these three criteria generally cannot be met
simultaneously by adjusting a single chemical or structural variable.
Nevertheless, the author argues that further increases in Tc at ambient
pressure should be possible, since a Tc of over 160 K has been achieved
at high pressure in the HgBa2Ca2Cu3O8+d (Hg-1223) compound, which has
buckled planes (19 refs.).
An overview of U/n processing has been prepared by R. Weinstein (TCSUH).
Adding uranium to HTS powders before texturing, and irradiating with
thermal neutrons n after texturing, produces effective pinning centers
and high Jcs for a variety of HTS systems. Fission of [235]^U produces
two high-energy high-Z ions, leaving tracks of aligned quasi-columnar
defects, which act as strong pinning centers. The author discusses
results of U/n processing in Y-123, Nd-123, Bi-2223/Ag tapes, and other
HTS systems (15 refs.).
Ph.D. Theses
Vortex dynamics and the vortex-lattice phase diagram in Bi2Sr2CaCu2O8+d
(Bi-2212) single crystals were studied in the Ph.D. thesis of B.
Khaykovich (Weizmann Institute). The author found that samples with
small critical current density in the central region and high critical
current density at the edges exhibited peculiar flux distributions
across the sample and unusual hysteresis loops. From studies of
unirradiated crystals and those irradiated by electrons or heavy ions,
the author concluded that vortex matter displays at least three distinct
phases: (a) a relatively ordered quasilattice at low fields, (b) a
highly disordered entangled vortex solid at fields above the second
magnetization peak, and (c) a liquid phase at high temperatures. The
author also carried out studies of the vortex-lattice melting transition
as a function of the angle of the applied magnetic field for Bi-2212
crystals containing columnar defects (207 refs.).
Studies of vortex dynamics and the vortex-matter phase diagram in high-
temperature superconductors also are reported in the Ph.D. thesis of D.
Fuchs (Weizmann Institute). The author carried out simultaneous Hall-
sensor measurements of magnetic fields and electrical transport in Bi-
2212 single crystals and found that the first-order phase transition of
the vortex matter displays both a magnetization step and a resistance
drop. Flux-transformer measurements performed close to Tc provided
evidence that the first-order transition is a sublimation transition.
Other experiments probing the current distribution revealed that many of
the transport measurements in Bi-2212 probe the physics of surface
barriers rather than the physics of bulk superconductors (189 refs.).
The Ph.D. thesis of P. Vanderbemden (Liege) reports studies of the
critical current density in bulk high-temperature superconductors as
determined by magnetic-flux-profile measuring methods. The author
presents (a) a theoretical discussion of flux-profile methods, (b) a
description of a practical realization of an experimental set-up
intended for measuring such flux profiles, and (c) a discussion of flux-
profile measurements in several bulk high-temperature superconductors,
including Y-123, Bi-2212, and Bi-2223 sintered ceramics and
polycrystalline textured Bi-2212 and Dy-123 (207 refs.).
The Houston Ph.D. thesis of W. Hennig describes how, by using YBa2Cu3O7-
d superconductors cooled to 77 K in the uniform 2.3 T field of an
electromagnet, magnetic levitation forces can be increased above those
produced by permanent magnets. The maximum trapped field at 77 K was
1.6 T, considerably higher than the field of 0.5 T that would be
produced by commonly used permanent ferromagnets of the size used in
this work. The author studied a number of levitation arrangements,
measured force-distance curves, and fitted these to phenomenological
models based on Bean's flux-pinning model (53 refs.).
Contributed by John R. Clem
Contents: Technology News is on page 7; Preprints begin on page 7;
Coming Events begin on page 12; and Resources are on page 13.
High-Tc Update is available without charge to interested persons.
Recipients are expected to participate in this information exchange by
sending us preprints, reprints, meeting news, research news, etc.
Contributions to defray the cost of newsletter printing and mailing are
welcome.
TECHNOLOGY NEWS
(Also see Applications section of Nota Bene.)
This section describes progress in manufacturing, product development,
and technology transfer in the high-Tc superconductivity field. Please
send your contributions (product development information, news regarding
technology transfer efforts, or any information you would like to share
about your corporation or laboratory) to the editor.
The new Australian Superconductors HTS plant (a division of Metal
Manufactures Limited) announced relocation of their high-temperature-
superconductor manufacturing pilot plant from the Australian Technology
Park in Sydney, into a new expanded facility on the recently opened
Engineering Innovation and Education Centre (EIEC) at the University of
Wollongong. The new facility will occupy 850 m2 and allow Australian
Superconductors to scale-up production capacity for its state-of-the-art
HTS tape, which includes tape made with different sheath alloys and with
tailored number and geometry of HTS filaments. The HTS tape is
optimized for minimal thermal and ac loss and maximum mechanical
strength, and developed specifically for each defined application. The
new plant will also increase the capability of Australian
Superconductors to manufacture and test its expanding range of HTS
products such as coils and current leads. The move to the EIEC is a key
part of the commercialization strategy since, earlier this year, Metal
Manufactures Ltd. signed an exclusive contract with the University to
jointly develop HTS tape and devices over the next three years. For
further information, contact Tim Beales, Manager, Australian
Superconductors, P.O. Box 21, Gloucester Boulevard, Port Kembla, NSW
2505, Australia; telephone +61 2 4221 5725; telefax +61 2 4221 5731; e-
mail tb1960@msn.com.au; Web site http://www. superconductors.com.au.
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.
A. A. Aligia, "Phase Diagram of the One-Dimensional Extended Attractive
Hubbard Model for Large Nearest-Neighbor Repulsion." Submitted to Phys.
Rev. B. Centro Atomico Bariloche and Instituto Balseiro, Comision
Nacional de Energia Atomica, 8400 Bariloche, ARGENTINA; e-mail
aligia@cab.cnea.gov.ar.
A. A. Aligia and Liliana Arrachea, "Triplet Superconductivity in Quasi
One-Dimensional Systems." To be published in Phys. Rev. B. Centro
Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia
Atomica, 8400 Bariloche, ARGENTINA; e-mail aligia@cab.cnea.gov.ar.
Liliana Arrachea and A. A. Aligia, "Pairing Correlations in a
Generalized Hubbard Model for the Cuprates." Submitted to Phys. Rev.
Lett. Contact A. A. Aligia, Centro Atomico Bariloche and Instituto
Balseiro, Comision Nacional de Energia Atomica, 8400 Bariloche,
ARGENTINA; e-mail aligia@cab.cnea.gov.ar.
P. Barbara, F. M. Araujo-Moreira, A. B. Cawthorne, and C. J. Lobb,
"Reentrant ac Magnetic Susceptibility in Josephson-Junction Arrays: An
Alternative Explanation for the Paramagnetic Meissner Effect." To be
published in Phys. Rev. B. Center for Superconductivity Research,
Department of Physics, University of Maryland, College Park, MD 20742-
4111; e-mail paola@squid.umd.edu; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9910088.
Manuel Cardona, "Raman Scattering in High Tc Superconductors: Phonons,
Electrons, and Magnons." To be published in Raman Scattering in Mater.
Sci.; edited by R. Merlin and W. H. Weber (Springer-Verlag). Max-
Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569
Stuttgart, GERMANY.
P. S. Czerwinka, R. P. Campion, K. F. Horbelt, P. J. King, S. Misat, S.
M. Morley, H.-U. Habermeier, and B. Leibold, "Investigations of the In-
Plane Anisotropy and the Critical Behavior of 10 degree-Tilted
YBa2Cu3O7-d Films Grown Upon (106) SrTiO3 Substrates." To be published
in Physica C (in press). Contact P. J. King, Department of Physics,
School of Physics and Astronomy, University of Nottingham, University
Park, Nottingham NG7 2RD, UNITED KINGDOM; telephone +44 115 951 5164;
telefax +44 115 951 5184; e-mail p.j.king@nottingham.ac.uk. Key words:
YBCO, miscut, dissipation, anisotropy, scaling, vortex glass.
J. Figueras, A. E. Carrillo, T. Puig, and X. Obradors, "Solubility Limit
and Anisotropy Analysis of Mg Doping in Melt Textured YBa2(Cu1-xMgx)3O7-
d." To be published in J. Low Temp. Phys. Institut de Ciencia de
Materials de Barcelona, C.S.I.C., Campus de la Universitat Autonoma de
Barcelona, E-08193 Bellaterra, SPAIN; telephone +34 93 580 1853; telefax
+34 93 580 5729. 74.72.Bk; 74.62.Bf; 74.60.Ec.
J. Fink, M. S. Golden, M. Knupfer, Th. Boeske, S. Haffner, R. Neudert,
S. Atzkern, C. Duerr, Z. Hu, S. Legner, T. Pichler, H. Rosner, S.-L.
Drechsler, R. Hayn, J. Malek, H. Eschrig, K. Ruck, and G. Krabbes, "The
Electronic Structure of High-Tc Superconductors: Introduction and
Recent Studies of Model Compounds." Presented at the NATO Adv. Study
Inst.-- Materials Science, Fundamental Properties and Future Electronic
Applications of High-Tc Supercond., Albena, Bulgaria, Sept. 14-25, 1998.
Institut fuer Festkoerper- und Werkstofforschung Dresden, Postfach
270016, D-01171 Dresden, GERMANY.
Dan T. Fuchs, "Study of Vortex Matter Phases and Phase Transitions in
Bi2Sr2CaCu2O8." Submitted as a Ph.D. thesis (Weizmann Institute of
Science). Department of Condensed Matter Physics, Weizmann Institute of
Science, Rehovot 76100, ISRAEL.
Yu. A. Genenko and H. C. Freyhardt, "Subcritical State of a
Superconductor Strip in a Magnetic Environment." Zentrum fuer
Funktionswerkstoffe GmbH Goettingen, Windausweg 2, D-37073 Goettingen,
GERMANY. 74.25.Ha; 74.60.Jg; 74.76.-w.
Yu. A. Genenko, A. Snezhko, and H. C. Freyhardt, "Magnetic Screening and
a Virgin Current-Carrying State of a Superconducting Sheet." Zentrum
fuer Funktionswerkstoffe GmbH Goettingen, Windausweg 2, D-37073
Goettingen, GERMANY.
Yu. A. Genenko, A. Usoskin, and H. C. Freyhardt, "Large Predicted Self-
Field Critical Current Enhancements in Superconducting Strips Using
Magnetic Screens." To be published in Phys. Rev. Lett. Zentrum fuer
Funktionswerkstoffe GmbH Goettingen, Windausweg 2, D-37073 Goettingen,
GERMANY. 74.25.Ha; 74.60.Jg; 74.76.-w.
D. A. Gorokhov and G. Blatter, "Hall Tunneling of Vortices in Superclean
Superconductors." Theoretische Physik, ETH-Hoenggerberg, CH-8093
Zurich, SWITZERLAND; e-mail gorokhov@itp.phys.ethz.ch; preprint also
available at http://xxx.lanl.gov/abs/cond-mat/9907469.
Yasumasa Hasegawa, Kazushige Machida, and Masa-aki Ozaki, "Spin Triplet
Superconductivity with Line Nodes in Sr2RuO4." Submitted to J. Phys.
Soc. Jpn. Faculty of Science, Himeji Institute of Technology, Kamigori,
Akou-gun, Hyogo 678-1297, JAPAN; telephone +81 791 58 0149; telefax +81
791 58 0132; e-mail hasegawa@sci.himeji-tech.ac.jp; preprint also
available at http://xxx.lanl.gov/abs/cond-mat/9909316. Key words:
spin-triplet superconductivity, line node of the energy gap, time-
reversal symmetry breaking.
T. Haugan, W. Wong-Ng, L. P. Cook, L. Swartzendruber, H. J. Brown, and
David T. Shaw, "Flux-Pinning of Bi2Sr2CaCu2O8+d High-Tc Superconducting
Tapes Utilizing (Sr,Ca)14Cu24O41+d and Sr2CaAl2O6 Defects." Submitted
to Ceramics Transaction. Division of Ceramics, Materials Science and
Engineering Laboratory, National Institute of Standards and Technology,
Stop 8520, 100 Bureau Dr., Gaithersburg, MD 20899; W. Wong-Ng's
telephone (301) 975-5791; telefax (301) 975-5334; e-mail winnie.wong-
ng@nist.gov.
Wolfgang Hennig, "Increase of Force in Magnetic Levitation by Using
Field Cooled YBa2Cu3O7-d Trapped Field Magnets Instead of Ferromagnets."
Submitted as a Ph.D. thesis (University of Houston). University of
Houston, 632 SR1, Houston, TX 77204-5506; telephone (713) 743-3600;
telefax (713) 747-4526; e-mail whennig@bayou.uh.edu.
W. Hennig, R. Weinstein, D. Parks, R.-P. Sawh, and Y. Ren, "Enhanced
Levitation Force Using YBa2Cu3Oy Trapped Field Magnets." Presented at
the 2nd Int. Workshop on the Proc. and Appl. of Supercond. (RE)BCO Large
Grain Materials, Morioka, Japan, Oct. 19-22, 1999. University of
Houston, 632 SR1, Houston, TX 77204-5506; telephone (713) 743-3600;
telefax (713) 747-4526; e-mail whennig@bayou.uh.edu.
R. P. Huebener, O. M. Stoll, A. Wehner, and M. Naito, "Nonlinear Vortex
Dynamics in the Cuprate Superconductor Nd2-xCexCuOy." Submitted to the
Proc. of the First Euroconf. on Vortex Matter in Superconductors, Crete,
Greece, Sept. 18-24, 1999; to be published in Physica C. Physikalisches
Institut, Lehrstuhl Experimentalphysik II, Universitaet Tuebingen,
Morgenstelle 14, D-72076 Tuebingen, GERMANY. 74.25.Fy; 74.60.Ge;
74.72.Jt.
G. A. Jorge and E. Rodriguez, "Twin Boundaries in YBa2Cu3O7 as Vortex-
Pinning Sites and Vortex-Flow Channels Observed Through ac Screening
Measurements." To be published in Phys. Rev. B. Contact E. Rodriguez,
Departamento de Fisica, Facultad de Ciencias Exactas y Naturales,
Universidad Nacional de Buenos Aires, Ciudad Universitaria, Pabellon I,
1428 Buenos Aires, ARGENTINA; e-mail eduardo@df.uba.ar. 74.60.Ge;
74.60.-w; 74.25.Dw.
James D. Jorgensen, "Key Insights from Structural Studies of High-
Temperature Superconductors: Is There a Path to Higher Tc?" To be
published in Advances in Supercond. XII: Proc. of the 12th Int. Symp.
on Superconductivity (ISS'99), Morioka, Japan, Oct. 17-19, 1999.
Materials Science Division and the Science and Technology Center for
Superconductivity, Argonne National Laboratory, 9700 South Cass Avenue,
Argonne, IL 60439; telephone (630) 252-8457; telefax (630) 252-7777.
Key words: crystal structure, maximum Tc, doping, electronic structure,
electronically driven structural instability.
E. Kandyel, S. Adachi, X.-J. Wu, and S. Tajima, "High Pressure Synthesis
of (La1-xSrx)8Cu8O20, (0.25 <= x <= 0.65) with a Wide Solubility Range
and High Cu Valence." To be published in J. Supercond.
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: layered compounds, 8-8-20, x-ray diffraction,
electrical properties.
E. Kandyel, X.-J. Wu, S. Adachi, and S. Tajima, "New Tl-Sr-Ca-Cu-O
Superconductor with 2223-Type Structure Stabilized by Mercury Under
High-Pressure." To be published in Physica C. Superconductivity
Research Laboratory, International Superconductivity Technology Center
(ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone
+81 3 3536-5703 through -5705; telefax +81 3 3536-5714 or -5717. Key
words: high-Tc superconductors, Tl/Sr-2223, Hg-doping, high-pressure
synthesis, magnetic susceptibility.
Boris Khaykovich, "Vortex Dynamics and Vortex-Matter Phase Transitions
in Bi2Sr2CaCu2O8 High-Temperature Superconductor." Submitted as a Ph.D.
thesis (Weizmann Institute of Science). Department of Condensed Matter
Physics, Weizmann Institute of Science, Rehovot 76100, ISRAEL; e-mail
fnboris@wis.weizmann.ac.il.
V. M. Krasnov, N. Mros, A. Yurgens, and D. Winkler, "Flux-Flow Branches
and Fiske Steps in Bi-2212 Mesas." Submitted to Physica B: Proc. of
the 22nd Int. Conf. on Low Temp. Phys. (LT22), Helsinki, Finland, Aug.
5-11, 1999. Department of Microelectronics and Nanoscience, Chalmers
University of Technology, S-41296 Goeteborg, SWEDEN; telephone +46 31
772 3397; telefax +46 31 772 3471; e-mail krasnov@fy.chalmers.se; Web
site http://fy.chalmers.se/~krasnov/.
V. M. Krasnov, V. A. Oboznov, V. V. Ryazanov, N. Mros, A. Yurgens, and
D. Winkler, "Comparison of Josephson Fluxon Modes in HTSC and LTSC
Stacked Josephson Junctions." Submitted to Phys. Rev. B. Department of
Microelectronics and Nanoscience, Chalmers University of Technology, S-
41296 Goeteborg, SWEDEN; telephone +46 31 772 3397; telefax +46 31 772
3471; e-mail krasnov@fy.chalmers.se; Web site
http://fy.chalmers.se/~krasnov/.
M.A.R. LeBlanc, David LeBlanc, Daniel S. M. Cameron, and Selahattin
Celebi, "Disclosure of Hidden Magnetic Moments in Low and High Tc
Hysteretic and Semi-Reversible Type II Superconductors During Warming to
Tc." To be published in Supercond. Sci. & Technol. Department of
Physics, University of Ottawa, Ottawa, Ontario, CANADA K1N 6N5.
74.60.Ge; 74.60.-w; 74.72.-h.
M.A.R. LeBlanc, Moh'd Rezeq, Daniel S. M. Cameron, and David LeBlanc,
"Comment on 'Angle Dependence of Magnetization in a Single-Domain
YBa2Cu3Ox Sphere.'" To be published in Phys. Rev. B. Department of
Physics, University of Ottawa, Ottawa, Ontario, CANADA K1N 6N5.
74.60.Ge; 74.25.Ha; 74.60.Ec; 74.72.-h.
Yijie Li, J. G. Wen, T. Utagawa, and K. Tanabe, "Effect of Deposition
Conditions and Annealing Process on Crystallinity and Superconducting
Properties of High-Tc Multilayers." To be published in Supercond. Sci.
& Technol. Superconductivity Research Laboratory, International
Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome,
Koto-ku, Tokyo 135-0062, JAPAN; telephone +81 3 3536-5703 through -5705;
telefax +81 3 3536-5714 or -5717.
W. Lo, N. Hari Babu, D. A. Cardwell, Y. Shi, and D. M. Astill,
"Fabrication and Characterization of Large NdBCO Grains Prepared Under
Low Oxygen Pressure." To be published in J. Mater. Res.
Interdisciplinary Research Centre in Superconductivity, University of
Cambridge, Madingley Road, Cambridge CB3 0HE, UNITED KINGDOM; D. A.
Cardwell's telephone +44 1223-337050 or -337076; telefax +44 1223-
337074; e-mail dc135@hermes.cam.ac.uk.
M. Lorenz, H. Hochmuth, D. Natusch, K. Kreher, T. Kaiser, R. Schwab, R.
Heidinger, C. Schaefer, G. Kaestner, and D. Hesse, "Highly Reproducible
Double-Sided Three-Inch Diameter YBCO and YBCO/SrTiO3/YBCO* Thin Films
for Microwave Applications." Presented at the Fourth European Conf. on
Appl. Supercond. (EUCAS'99), Barcelona, Spain, Sept. 14-17, 1999.
Fakultaet fuer Physik und Geowissenschaften, Universitaet Leipzig,
Linnestr. 5, D-04103 Leipzig, GERMANY; e-mail mlorenz@physik.uni-
leipzig.de.
Frank Ludwig and Dietmar Drung, "Low-Frequency Noise of Improved Direct-
Coupled High-Tc Superconducting Quantum Interference Device
Magnetometers in ac and dc Magnetic Fields." To be published in Appl.
Phys. Lett. Section Cryosensors, Physikalisch-Technische Bundesanstalt,
Abbestrasse 2-12, D-10587 Berlin, GERMANY; telephone +49 30 3481 434;
telefax +49 30 3481 490; e-mail frank.ludwig@ptb.de.
M. T. Malachevsky and D. A. Esparza, "Metal-Ceramic Interface Response
to Bending and Fatigue Cycles in Superconducting Ag-Bi2223 Composites."
To be published in Physica C. Complejo Tecnologico Pilcaniyeu, Comision
Nacional de Energia Atomica, Av. Bustillo 9500, 8400 San Carlos de
Bariloche, ARGENTINA; e-mail malache@cab.cnea.gov.ar. Key words: Ag-
Bi2223 composites, bending cycles, fatigue, cracks formation. 74.72.Hs;
74.25.Ld; 62.20.Mk; 74.60.Jg.
Roman G. Mints, Vladimir G. Kogan, and John R. Clem, "Vortices in
Magnetically Coupled Superconducting Layered Systems." To be published
in Phys. Rev. B. Contact Vladimir G. Kogan, Ames Laboratory-USDOE and
Department of Physics, Iowa State University, Ames, IA 50011-3020;
telephone (515) 294-8080; telefax (515) 294-0689; e-mail
kogan@ameslab.gov; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9910063. 74.60.-w; 74.80.Dm.
O. V. Misochko, "Temperature Dependence of Electronic Raman Scattering
as a Probe of Pairing Symmetry in High-Tc Superconductors." To be
published in Solid State Commun. Institute of Solid State Physics,
Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region,
RUSSIA; e-mail misochko@issp.ac.ru. Key words: superconductors,
optical properties, inelastic light scattering.
Arianna Montorsi and Vittorio Penna, "Spin Picture of the One-
Dimensional Hubbard Model: Two-Fluid Structure and Phase Dynamics." To
be published in Phys. Rev. B. Dipartimento di Fisica, INFM, Politecnico
di Torino, I-10129 Torino, ITALY; Vittorio Penna's e-mail
penna@athena.polito.it; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9909435.
A. Mourachkine, "The Symmetries and Origins of the Order Parameters for
Pairing and Phase Coherence in Cuprates." Service de Physique des
Solides, Universite Libre de Bruxelles, CP233, Boulevard du Triomphe, B-
1050 Brussels, BELGIUM; telephone +32 2 650 5751; telefax +32 2 650
5916; e-mail anmourac@ulb.ac.be; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9909430.
Katsu Ohnishi, Kazunori Miyahara, and Youichi Enomoto, "Characteristics
of NdBa2Cu3O7-d Josephson Junctions Fabricated by Deca-Nanoscale Focused
Ion Beam." To be published in Jpn. J. Appl. Phys. Superconductivity
Research Laboratory, International Superconductivity Technology Center
(ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135, JAPAN; telephone
+81 3 3536-5703 through -5705; telefax +81 3 3536-5714 or -5717. Key
words: focused ion beam, Josephson junction, distribution
characteristics, oxide superconductor, grain boundary, NdBa2Cu3O7-d.
Mi-Ae Park and Yong-Jihn Kim, "Weak Localization Effect in
Superconductors by Radiation Damage." Department of Physics, University
of Puerto Rico at Humacao, Humacao, Puerto Rico 00791; Yong-Jihn Kim's
e-mail at Bilkent University, Turkey yjkim@fen216.fen.bilkent.edu.tr;
preprint also available at http://xxx.lanl.gov/abs/cond-mat/9909358.
74.20.-z; 74.40.+k; 74.90.+n.
T. Puig, F. Galante, E. M. Gonzalez, J. L. Vicent, B. Martinez, and X.
Obradors, "Vortex Liquid Entanglement in Twinned YBa2Cu3O7/Y2BaCuO5
Composite Superconductors." To be published in Phys. Rev. B (in press).
Institut de Ciencia de Materials de Barcelona, C.S.I.C., Campus de la
Universitat Autonoma de Barcelona, E-08193 Bellaterra, SPAIN; telephone
+34 93 580 1853; telefax +34 93 580 5729. 74.25.Fy; 74.60.Ec; 74.60.Ge;
74.72.Bk.
A. Sacuto, J. Cayssol, D. Colson, and P. Monod, "Electronic Raman
Scattering on Underdoped Hg-1223 High-Tc Superconductors:
Investigations on the Symmetry of the Order Parameter." Laboratoire de
Physique de la Matiere Condensee, Ecole Normale Superieure, 24 Rue
Lhomond, F-75231 Paris Cedex 05, FRANCE; telephone +33 1 4329 1225;
telefax +33 1 4587 3489; e-mail alsa@physique.ens.fr; preprint also
available at http://xxx.lanl.gov/abs/cond-mat/9909267.
S. Sarkar, D. Pal, S. S. Banerjee, S. Ramakrishnan, A. K. Grover, C. V.
Tomy, G. Ravikumar, P. K. Mishra, V. C. Sahni, G. Balakrishnan, D. McK.
Paul, and S. Bhattacharya, "Peak Effect in Ca3Rh4Sn13: Vortex Phase
Diagram and Evidences for Stepwise Amorphization of Flux Line Lattice."
Department of Condensed Matter Physics and Material Science, Tata
Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai
400005, INDIA; e-mail shampa@tifr.res.in; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9909297. Key words: peak effect,
order-to-disorder transformation, vortex phase diagram, Ca3Rh4Sn13.
64.70.Dv; 74.60.Ge; 74.25.Dw; 74.60.Ec; 74.60.Jg.
V. Selvamanickam, G. Galinski, G. Carota, J. DeFrank, C. Trautwein, P.
Haldar, U. Balachandran, M. Chudzik, J. Y. Coulter, P. N. Arendt, S. R.
Foltyn, B. Newnam, and D. E. Peterson, "High-Current Y-Ba-Cu-O Conductor
by Metal Organic Chemical Vapor Deposition on Metal Substrates."
Submitted to Supercond. Sci. & Technol. Intermagnetics General
Corporation, Latham, NY 12110; preprint also available from 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. Key words: YBCO, superconductor,
MOCVD, IBAD, current density.
C. T. Shih, Y. C. Chen, and T. K. Lee, "Numerical Study of the Pairing
Correlation of the t-J Type Models." National Center for High-
Performance Computing, Hsinchu, Taiwan, REPUBLIC OF CHINA; telephone
+886 3 577 6085; e-mail c00cts00@nchc.gov.tw; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9910107. 74.20.-z; 71.27.+a; 74.25.Dw.
T. Stein, G. A. Levin, C. C. Almasan, D. A. Gajewski, and M. B. Maple,
"Dynamics of Flux Creep in Underdoped Single Crystals of Y1-
xPrxBa2Cu3O7-d." Department of Physics, Kent State University, Kent, OH
44242; e-mail phyxs722@zeus.kent.edu; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9910174.
Philippe Vanderbemden, "Determination of Critical Current in Bulk High-
Temperature Superconductors by Magnetic Flux Profile Measuring Methods."
Submitted as a Ph.D. thesis (Universite de Liege). Institut
D'Electricite Montefiore, SUPRAS, Universite de Liege, Sart-Tilman B28,
B-4000 Liege, BELGIUM; telephone +32 4366 2674; telefax +32 4366 2877;
e-mail vanderbe@montefiore.ulg.ac.be.
N. Vasanthamohan, T. B. Peterson, J. P. Singh, V. K. Vlasko-Vlasov, U.
Welp, M. T. Lanagan, and G. W. Crabtree, "Effect of Core Inhomogeneity
on Strain Tolerance of Bi-2223 Composite Conductors." Submitted to J.
Appl. Phys. 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.
J. P. Wallington and James F. Annett, "BCS to Bose Crossover in
Anisotropic Superconductors." H. H. Wills Physics Laboratory,
University of Bristol, Royal Fort, Tyndall Avenue, Bristol BS8 1TL,
UNITED KINGDOM; e-mail jon.wallington@bristol.ac.uk; preprint also
available at http://xxx.lanl.gov/abs/cond-mat/9909043.
Qiang-Hua Wang and Z. D. Wang, "Zeeman Coupling and Abnormal Thermal
Conductivities in BSCCO Superconductors." Department of Physics and
National Laboratory of Solid State Microstructures, Nanjing University,
Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA; e-mail
qhwang@bohr.physics.hku.hk; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9909399. 74.20.De; 74.25.Fy; 74.60.Ec.
Roy Weinstein, "An Overview of U/n Processing." Presented at the 12th
Int. Symp. on Superconductivity (ISS'99), Morioka, Japan, Oct. 17-19,
1999. Department of Physics and Texas Center for Superconductivity,
University of Houston, Houston, TX 77204-5506; telephone (713) 743-8200;
telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu. Key words:
pinning centers, high Jc, high H_[irr], isotropy, fission damage.
W. Wong-Ng, J. P. Cline, L. P. Cook, and W. Greenwood, "X-ray
Characterization of Compounds in the SrO-PbO System." To be published
in Adv. X-ray Anal. A256 MATLS, National Institute of Standards and
Technology, Gaithersburg, MD 20899; telephone (301) 975-5791; telefax
(301) 975-5334; e-mail winnie.wong-ng@nist.gov.
W. Wong-Ng and L. P. Cook, "Melting Equilibria of the 2223 [(Bi,Pb)-Sr-
Ca-Cu] High Tc Superconductor in Oxygen." Submitted to Ceramics
Transaction. A256 MATLS, National Institute of Standards and
Technology, Gaithersburg, MD 20899; telephone (301) 975-5791; telefax
(301) 975-5334; e-mail winnie.wong-ng@nist.gov.
W. Wong-Ng, L. P. Cook, W. Greenwood, and A. Kearsley, "Effect of Ag on
the Primary Phase Field of High Tc (Bi,Pb)-2223 Superconductor."
Submitted to J. Mater. Res. A256 MATLS, National Institute of Standards
and Technology, Gaithersburg, MD 20899; telephone (301) 975-5791;
telefax (301) 975-5334; e-mail winnie.wong-ng@nist.gov.
W. Wong-Ng, J. Dillingham, and L. P. Cook, "Phase Relations of the SrO-
Ho2O3-CuOx System." To be published in J. Solid State Chem. A256
MATLS, National Institute of Standards and Technology, Gaithersburg, MD
20899; telephone (301) 975-5791; telefax (301) 975-5334; e-mail
winnie.wong-ng@nist.gov.
W. Wong-Ng, J. A. Kaduk, W. Greenwood, and J. Dillingham, "Powder X-ray
Reference Patterns of Sr2RGaCu2O7 (R=Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm,
Yb and Y)." To be published in J. Res. Nat. Inst. Stand. Technol.
A256 MATLS, National Institute of Standards and Technology,
Gaithersburg, MD 20899; telephone (301) 975-5791; telefax (301) 975-
5334; e-mail winnie.wong-ng@nist.gov.
Z. A. Xu, N. P. Ong, T. Noda, H. Eisaki, and S. Uchida, "Anisotropic
Effect of Field on the Orthorhombic-to-Tetragonal Transition in the
Striped Cuprate (La,Nd)2-xSrxCuO4." Submitted to Europhys. Lett.
Joseph Henry Laboratories of Physics, Princeton University, Princeton,
NJ 08544; e-mail zhuan@princeton.edu; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9910123.
Jiro Yamada, V. V. Srinivasu, Masaki Tada, Ken-ichi Itoh, Akinori
Hashizume, Ikutaro Kometani, Khairil Anwar, and Tamio Endo, "Influence
of dc Field Sweep Rate on Non-Resonant Microwave Absorption in a
YBa2Cu3Ox Superconductor." Presented at the 12th Int. Symp. on
Superconductivity (ISS'99), Morioka, Japan, Oct. 17-19, 1999. Contact
Tamio Endo, Department of Electrical and Electronic Engineering, Mie
University, 1515 Kamihama, Tsu 514, JAPAN; telephone +81 592 32 1211;
telefax +81 592 31 9471; e-mail endo@cm.elec.mie-u.ac.jp. Key words:
microwave absorption, YBa2Cu3Ox superconductor, vortex dynamics.
A. Yamamoto, T. Furumochi, and S. Tajima, "Metal-Insulator Transition
and Superconductivity in Sr and La Substituted BaPb1-xBixO3." To be
published in Physica C. Superconductivity Research Laboratory,
International Superconductivity Technology Center (ISTEC), 10-13
Shinonome 1-chome, Koto-ku, Tokyo 135-0062, JAPAN; telefax +81 3 3536
5714; e-mail yamamoto@istec.or.jp. Key words: superconductivity,
metal-insulator transition, transport properties, BPBO.
In-Sang Yang, M. V. Klein, S. L. Cooper, P. C. Canfield, B. K. Cho, and
Sung-Ik Lee, "A Study of the Superconducting Gap in RNi2B2C (R=Y,Lu)
Single Crystals by Inelastic Light Scattering." Materials Research
Laboratory, Department of Physics, University of Illinois at Urbana-
Champaign, Urbana, IL 61801; e-mail iyang@uiuc.edu; preprint also
available at http://xxx.lanl.gov/abs/cond-mat/9910087. Key words:
borocarbide superconductors, superconducting gap, electronic Raman
scattering. 78.30.Er; 74.70.Dd; 74.25.Jb.
Y. G. Zhao, M. Rajeswari, R. C. Srivastava, Z. W. Dong, R. P. Sharma,
and T. Venkatesan, "Growth and Electrical Properties of PrSr2Cu3O7-d
Thin Films." To be published in Physica C (in press). Center for
Superconductivity Research, Department of Physics, University of
Maryland, College Park, MD 20742; telephone (301) 405-7654; telefax
(301) 405-3779; e-mail yzhao@squid.umd.edu. Key words: PrSr2Cu3O7-d,
PLD, thin films. 74.72.Bk; 74.25.Fy; 74.76.-w.
Jian-Xin Zhu, T. K. Lee, C. S. Ting, and Chia-Ren Hu, "Unified Theory of
Quasiparticle Resonant States Induced by a Unitary Impurity in a d-Wave
Superconductor." Department of Physics and Texas Center for
Superconductivity, University of Houston, Houston, TX 77204-5932;
telephone (713) 743-8276; telefax (713) 743-8201; e-mail
jxzhu@mira.tcs.uh.edu; preprint also available at
http://xxx.lanl.gov/abs/cond-mat/9909363. 74.25.Jb; 74.50.+r; 73.20.Hb.
A. A. Zhukov, S. Kokkaliaris, P.A.J. de Groot, M. J. Higgins, S.
Bhattacharya, R. Gagnon, L. Taillefer, "Negative Dynamic Creep in the
Peak-Effect Regime in Type II Superconductors." Submitted to Phys. Rev.
Lett. Department of Physics and Astronomy, University of Southampton,
Southampton SO17 1BJ, UNITED KINGDOM; telephone +44 1703 592077; telefax
+44 1703 593910; e-mail aaz@phys.soton.ac.uk. 74.60.Ge; 74.60.Jg;
74.72.Bk.
Marco Zoli, "Dispersive Holstein Model: Which Mass for the Small
Polaron?" To be published in Physica C (in press). Dipartimento di
Matematica e Fisica, Istituto Nazionale di Fisica della Materia,
Universita di Camerino, Via Madonna delle Carceri, I-62032 Camerino,
ITALY; telefax +39 0737 40042; e-mail zoli@campus.unicam.it. Key words:
high-Tc superconductivity, polaron mass, electron-phonon coupling.
71.38.+i; 71.28.+d; 74.20.Mn; 74.25.Kc.
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.)
March 13 - 17, 2000: 18th General Conference of the Condensed Matter
Division of the European Physical Society (EPS CMD18-2000), Montreux,
Switzerland. Conference will consist of plenary and invited talks, mini
colloquia, and poster sessions on topics covering condensed-matter
physics. Format will be similar to that of the last EPS-CMD17
conference in Grenoble (1998). The program of each mini colloquium is
organized by its respective chairpersons. No proceedings will be
published. Will include exhibition of scientific instruments and books.
Abstract deadline, November 15, 1999. For information, contact
Conference Secretariat CMD18-2000, Laboratorium fuer Festkoerperphysik,
ETH Hoenggerberg, CH-8093 Zurich, Switzerland; e-mail eps-cmd18@psi.ch;
Web site www.eps-cmd18.ch.
*March 20 - 24, 2000: 2000 March Meeting, Minneapolis Convention
Center, Minneapolis, Minn. Sessions on superconductivity will include
the following topics: synthesis, growth, and processing (bulk and
films); thermodynamic and transport properties; mechanical and
structural properties; electronic structure and spectroscopic
properties; flux pinning and flux dynamics; spin properties (NMR, NQR,
etc.); tunnel junctions, devices, and Josephson arrays; quantum
computing; and other focused sessions. Abstract deadline, December 3,
1999. (Complete abstract submission instructions can be found at
http://www.aps.org/meet/meet-abstract.html.) For further general
information, contact Donna Baudrau, Manager, APS Meetings Department,
telephone (301) 209-3285, e-mail baudrau@aps.org; more information on
the March meeting is available at the Web site
http://www.aps.org/meet/MAR00/.
*March 31 - April 10, 2000: Conference on Major Trends in
Superconductivity in the New Millennium (MTSC 2000) and Symposium on
Itinerant and Localized States in HTSC (SILS), Klosters, Kanton
Graubuenden, Switzerland. Scope of MTSC 2000 is on recent developments
and trends in new superconducting systems with emphasis on experiments
and theories which are relevant to the pairing mechanism. Besides the
superconducting cuprates, conventional superconductors, organic systems,
borocarbides, ruthenates, nanostructures, and fullerenes will be
addressed. In order to raise the awareness for novel ideas and results
in this rapidly growing field, the physics and chemistry of related
materials will be included. Special emphasis on phenomena related to
nanoscale phase separation and charge modulation. Symposium on
Itinerant and Localized States in HTSC (SILS) will focus on large and
small polaron and bipolaron effects in high-Tc materials with special
emphasis on their preparative properties. MTSC 2000 is organized in
close analogy to the Gordon conferences. Limited number of slots for
posters. Total number of participants limited to 130 persons.
Proceedings will be published in a special issue of Journal of
Superconductivity. Abstract and pre-registration deadline, November 15,
1999. For more information, contact Annette Bussmann-Holder, Max-
Planck-Institut fuer Festkoerperforschung, Heisenbergstr. 1, D-70569
Stuttgart, Germany; telephone +49 711 689 1679; telefax +49 711 689
1091. Or contact Vladimir Z. Kresin, Lawrence Berkeley Laboratory,
University of California, 1 Cyclotron Road, Berkeley CA 94720; telephone
(510) 486-6951; telefax (510) 486-5401. Information also available at
Web site http://www.mpi-stuttgart.mpg.de/CONF/mtsc2000.html.
*April 24 - 28, 2000: Superconducting and Related Oxides -- Physics and
Nanoengineering IV, Marriott's Orlando World Center Resort and
Convention Center, Orlando, Fla. Part of SPIE's 2000 AeroSense
Symposium. Fourth in the series of SPIE conferences focused on basic
issues in physics and materials science of high-temperature
superconductors and related compounds that may be relevant for their
applications in electronics, optics, and optoelectronics. Topics are:
a) structural, transport, magnetic, and thermal properties of thin films
of cuprates and related compounds; b) homoepitaxy, new substrate
materials, epitaxial and morphological properties, interface smoothness
and disorder, layer thickness fluctuations, interdiffusion, and strain;
c) proximity effects, surface and interface effects, and superconductors
in contact with insulators, semiconductors, normal metals, ferro- and
antiferromagnets, piezoelectrics, etc.; d) search for novel high-
temperature superconducting phases by atomic engineering; e) electronic
structure, charge redistribution, localization, single-particle and
collective excitations, and Josephson phenomena in natural and
artificial superlattices; f) novel device concepts, electric field
effect in heterostruc-tures, hybrid optoelectronic devices, and
cryoelectronics. Three-day exhibition. Proceedings to be published.
Contact SPIE, P.O. Box 10, Bellingham, WA 98227-0010; telephone (360)
676-3290; telefax (360) 647-1445; e-mail OR@spie.org; Web site
http://www.spie.org/web/meetings/calls/or00/confs/OR15.html.
*April 30 - May 3, 2000: 102nd Annual Meeting & Exposition Gateway to
the New Millennium, St. Louis, Mo. This is the premier inter-national
forum for ceramics. Comprehensive coverage of ceramic and materials
science, engineering, technology, manufacturing, and applications. The
program will include symposia and focused programs: the symposia are
designed to provide multidisciplinary perspectives on the nature and
impact of state-of-the-art ceramic science, engineering, and technology
in key areas, and the focused programming provides forums for in-depth
technical exchange on specialized topics. Symposia will include ceramics
and integrated components in microelectronics, optoelectronics, wireless
communications and consumer electronics; ceramics for biological,
chemical, mechanical, thermal and high-radiation applications;
processing of ceramics; and cross-cutting symposia. Abstract deadline,
November 15, 1999. For information, contact The American Ceramic
Society, P.O. Box 6136, Westerville, OH 43086-6136; telephone (614) 890-
4700; telefax (614) 899-6109; e-mail info@acers.org; Web site
http://www.acers.org/.
*June 18 - 23, 2000: European Conference on Energy Dispersive X-Ray
Spectrometry (EDXRS 2000), Krakow, Poland. Aim of the conference is to
bring together scientists working either in basic research in x-ray
spectrometry, detectors and sources, or involved in applications of x-
ray spectrometry or some of the related experimental techniques. Main
topics: interaction of photons and particles with matter and modeling;
new developments in instrumentation (instruments utilizing polarized
radiation, synchrotron radiation and other x-ray sources, grazing angle
spectrometers, portable instruments); energy dispersive x-ray detectors
(cryo-detectors, low-Z detectors, Peltier-cooled detectors, dedicated
pulse processing); quantitation and data handling (sample preparation,
quality control and quality assurance, simulation, modeling, software);
x-ray optics (capillaries, mirrors, multilayers, TXRF, imaging);
microanalysis and elemental mapping (micro-XRF, micro-PIXE, EPMA); and
x-ray spectrometry applications in life and environmental sciences,
earth sciences, art and cultural heritage, material sciences, and
industry. Pre-registration deadline, November 15, 1999; abstract
deadline, March 1, 2000. The official language of the conference is
English. For information, contact EDXRS-2000 Secretariat, Faculty of
Physics and Nuclear Techniques, University of Mining and Metallurgy, Al.
Mickiewicza 30, 30-059 Krakow, Poland; telefax +48 12 6340010; Web site
http://www.ftj.agh.edu.pl/wfitj/conf/edxrs/.
RESOURCES
Information
Proceedings: High Temperature Super-conductivity -- proceedings of the
1999 University of Miami Conference, Coral Gables, Florida, January 7-
13, 1999, edited by Stewart E. Barnes, Joseph Ashkenazi, Joshua Cohn,
and Fulin Zuo. AIP Conference Proceedings 483. Physical properties,
microscopic theory, mechanisms for high-temperature superconductivity,
and related topics (e.g., ladders, manganites, nickelates) are covered.
Recent important experimental and theoretical developments in high-
temperature superconductivity are discussed. Publ. 1999; 450 pp.; price
$130; ISBN 1-56396-880-0. For U.S. orders, contact Springer-Verlag New
York, P.O. Box 2485, Secaucus, NJ 07096; telephone (800) SPRINGER (777-
4643); telefax (201) 348-4505. For orders outside the U.S. and Canada,
contact Springer-Verlag Berlin, P.O. Box 31 13 40, D-10643 Berlin,
Germany; telephone +49 30 82787 0; telefax +49 30 82787 301; e-mail
orders@springer.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. 13, #21, November 1, 1999.