Oxygen Interstitial Dynamics in Bi(2)Sr(2)CaCu(2)O(8+delta) Oxides Measured by Mechanical Spectroscopy

Many researchers became interested in the discovery of Bi(2)Sr(2)CaCu(2)O(8+delta) oxides with critical temperature of around 80 K. It is known that the critical temperature is related to the CuO2 planes of the material. For this reason, the study of the interstitial oxygen in these oxides is of great relevance. The samples were prepared by means of conventional solid state reactions, through the stoichiometric mixture of precursory powders. After the sinterization, the samples were submitted to measurements of density, electrical resistivity, x-ray diffraction, scanning electron microscopy and energy dispersion spectroscopy, with the objective of performing their characterization. The measurements of mechanical spectroscopy were performed by a torsion pendulum. The results show three relaxation processes in the temperature range of 200 and 700 K, with activation energy of approximately 0.9 eV, which has been attributed to the dynamics of the interstitial oxygen present in the material.

Vortex-Antivortex Dynamics in a Mesoscopic Superconducting Prism with a Centered Antidot

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Vortex dynamics in mesoscopic superconducting square of variable surface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Oxygen dynamics and the effects of heat treatments in SBCO samples investigated by mechanical spectroscopy

The compound SmBa(2)Cu(3)O(7-delta) (SBCO)-obtained by substituting rare-earth Sm for Y in the well-known and most studied YBa(2)Cu(3)O(6+delta) (YBCO)-is potentially attractive to study in order to understand the superconductivity mechanism in physics and in electronic device applications. For SBCO, the possibility of variable stoichiometry and the high mobility of oxygen in CuO(x) planes give rise to a rich phase diagram. This study reports on the effect of heat treatments in an oxygen atmosphere on the anelastic properties of this oxide, in which relaxation processes were observed, attributed to oxygen atom jumps present in the Cu-O planes during the orthorhombic phase.

Surface effects on vortex dynamics in thin type-II superconducting stripes with random pinning

We analyze the dynamics of a driven vortex lattice moving in a thin Superconducting stripe. The two dimensional stripe is assumed to be finite in the longitudinal direction, where we take into account the Surface effects, and infinite in the transversal direction. The numerical simulations are performed using the Langevin dynamics, including the vortex-vortex interaction, interaction of vortices with the surface current, vortex images, transport current and randomly distributed pinning centers. We show results for the differential resistivity and the vortex trajectories as a function of the external force. (C) 2004 Elsevier B.V. All rights reserved.