[en] Short note

[en] The experimental techniques and results of surface Z_c measurements between 100 MHz and GHz and between 4.2 and 300 K on oxide superconductor samples are reviewed. For YBa₂Cu₃O_7-σ polycrystalline bulk samples and thick films on silver substrates partially c-axis textured in high magnetic fields have been investigated as well as single crystals and highly oriented thin films on various dielectric substrates. A significant increase of R_s at high microwave field levels is only observed for granular samples, but no breakdown of the superconducting state occurs up to 64mT

[en] Short note

[en] The model of superconductivity is considered taking into account the overlap and correlation effects in ρ- or S-shells of electronegative ions O^2- and H^- in the rigid lattice formed by other elements in the oxygen and hydrogen related compounds. Pairing force within the model arises as a consequence of orbital size dependence upon its filling and is characteristic for the above 'electronegative' metals with moderate overlap between hole orbitals

[en] The two-band superconductor model is discussed for its possible application in treating the kinetic properties of high-temperature superconductors (HTSC) in the normal state. Specific properties of relaxation processes in the electron system of a narrow-band conductor are found. The temperature dependence of resistance resulted from the interference of various relaxation mechanisms has an abnormally high value that changes in sign with variations in temperature and electron concentration. Kinetic and thermodynamic properties of the two-band model are correlated for different values of its microscopic parameters

[en] The temperature dependence of heat capacity of a layered crystal CsDy(MoO₄)₂ is studied experimentally in a temperature range of 1.5 to 20 K. Contributions to the specimen heat capacity in a transition region of magnetic transition (T_c < or approx. 1.5 K) are found. The data on low-temperature lattice heat capacity permit the Debye temperature to be estimated

[en] It is shown that the nonlinearity of voltage-current characteristics (IVC) of superconducting point contacts enables one, as in the case of tunnel junctions, to obtain the energy dependence of the order parameter and to restore the function of the electron-phonon interaction (EPI) by reciprocating the Eliashberg equations. The effect of the electron spectrum renormalization due to EPI upon the steady-state IVC of the S-c-N contact is studied. This is found to lead to nonlinear conductivity showing up as maxima in the region of typical phonon energies. The correction for the point contact current found, which reflects the elastic scattering of electrons by non-equilibrium phonons generated by the electron flow in the region of microconstriction. This addition fixed phonons in the vicinity of spectral Van-Hove points of the phonon spectrum

[en] By means of the Moessbauer effect and the electric resistivity and magnetic susceptibility measurements of iron-doped lanthanum-strontium ceramics, it is found that the superconducting transition is suppressed by magnetic ordening

[en] It is found that YBA₂Cu₃O_7-δ ceramics displays acoustic emission signals with temperature range 40-280 K. The correlation is found to exist between the temperature hysteresis of transport acoustic characteristics and AE peaks

[en] Nonlinear excitations in layered superconducting structures representing the system of interacting parallel long Josephson junctions are investigated. It is shown that the propagation of dynamic supersolitons (localized excitations of the density of vortex lattice) is quite possible in such a system. Two types of the soliton excitations are considered in terms of the effective equations of the dynamics of fluxon lattice in magnetic field. These are kinks whose propagation is related to magnetic flux transport across superconducting layers, and envelope solitons. The dynamic kink relaxation is studied numerically