[en] The present invention describes the fabrication process of an electric circuit element in a multi-layer orientated texture type 2 superconductor, in reversible magnetization field conditions. Element great axis is orthogonal to the c cristallographic axis of the superconductive phase, with electrical input and output contacts on each layer. 5 refs., 6 figs

[en] The authors developed a new six-face lithography technique on very small Y-123 single crystals, in order to obtain a current flow parallel to a unique crystallographic direction. Using this technique, they observe that the broadening of the resistive transition along the c-axis of a Y-123 single crystal in the presence of strong magnetic fields (H > H_c1) parallel ab disappears below a well defined line in the H-T phase diagram. Above this line, dissipation is ohmic and field dependent. Below this line, a discontinuity appears in the resistivity curves, and the I-V behavior is strongly non linear. The shape of the resistive transition below the T_m(H) line has a universal character, which remains unaffected by changes in the amplitude of the field. This unusual behavior contradicts any collective flux pinning model which predicts a field dependent activation energy and suggests a phase transition related to the depinning line

[en] The spin fluctuations in the normal state of the unconventional superconductor Sr₂RuO₄ have been studied using inelastic neutron scattering with polarization analysis on single crystals. We find that the spin fluctuations are anisotropic with χ_c/χ_ab=2.0±0.4. No evidence for Q-independent or nearly-ferromagnetic spin fluctuations are found in the energy range 4-22 meV, in contradiction with NMR measurements

[en] Extensive magnetization and magnetoresistivity experiments on CeRu₂Si₂ are described, with special emphasis on the metamagnetic-like transition that occurs at H* = 80 kOe. By contrast to the low-field susceptibility, the differential susceptibility at H* almost diverges at T → O. It is suggested that high magnetic fields (H > H*) restore a situation where the interactions between particles have collapsed. Comparison is made with other well-known examples: TiBe₂, UPt₃, TmSe, and ³He

[en] Sr₂RuO₄ is an unconventional superconductor with a superconducting transition temperature of ∼1.5 K. The formation of vortex chains in Sr₂RuO₄ is observed, they have been directly imaged by μSQUID force microscopy at low temperature. Ginzburg-Landau theory for anisotropic superconductors is in qualitative agreement with the observed dependencies of the vortex chains on the variation of the tilting angle or the amplitude of the external magnetic field

[en] The superconducting properties of the Mosub(2-x)Msub(x)BC borocarbides (M equivalent to Zr, Nb, Rh, Hf, Ta, W) are reported. They have an Mo₂BC-type structure with orthorhombic symmetry and the space group Cmcm. Stoichiometric powder samples were prepared by arc melting. A large single crystal of Mo₂BC was obtained by a Czochralski-type method. The upper limit of x depends mainly on the size of the M atoms. A study of the magnetization as a function of field at different temperatures shows that all borocarbides are type II superconductors. Resistivity measurements give generally a critical temperature Tsub(cr) above 4.2 K. Tsub(cr) and the critical fields Hsub(c2) increase for rhodium substitution but decrease in other cases. For comparison the superconducting properties are discussed in terms of the valence electron concentration and the molar volume. (Auth.)

[en] We report magnetostriction measurements on Pr_0.65Ca_0.35MnO₃ polycrystalline samples in magnetic fields up to 14 T. The charge ordering occurs below T_CO=230 K. The application of a magnetic field causes the transition from the ordered insulator state to metallic state. It is found that this insulator-metal transition is accompanied by large negative jumps in the longitudinal and transverse magnetostrictions with a temperature-dependent hysteresis. The H-T phase diagram is determined from the magnetostriction

[en] New ternary silicides LaRhSi, LaIrSi and NdIrSi have been synthesized by arc melting. On the basis of the ZrOS structure, their powder patterns have been indexed using a primitive cubic unit cell with space group P2₁3. LaRhSi and LaIrSi have a superconducting transition at 4.35K and 2.3K respectively. NdIrSi shows spontaneous magnetization below Tsub(C) = 10K and its magnetic structure is probably non colinear. (author)

[en] New superconducting ternary silicides LaRhSi₃ and LaIrSi₃ have been prepared by arc melting from the elements and annealing for ten days at 900⁰C. A single crystal study shows these materials to be of tetragonal symmetry and isostructural with BaPtSn₃. Their superconducting transition temperature which depends strongly on stoichiometry and thermal treatment occurs between 1.9 and 2.7 K. The structures have been compared to those of the superconducting compounds LaRh₂Si₂ and La₂Rh₃Si₅. The occurrence of superconductivity in these materials seems to be related to the presence of similar coordination polyhedra for Rh or Ir and Si atoms

[en] We have developed a new technique to directly measure ρ_c and ρ_ab of very small single crystals of Y₁Ba₂Cu₃O_7-x. We used this technique to measure ρ_c in two different crystals having different Tc's. In contrast with results obtained by the standard Montgomery method we find smaller values of ρ_c at 300 K, although the increase of ρ_c at T≥Tc is higher. Our data indicate the presence of localized states between the CuO₂ planes due to intrinsic or extrinsic ''dirty'' interlayers. The c-axis resistivity follows a thermally activated law lnρ_c∝(T₀/T) with T₀=410 K. A correlation is observed between the lowering of Tc and the increase of ρ_c at T≥Tc. (orig.)