Magnetoresistivity measurements in HTC superconductors: layered behavior and vortex-glass-to-liquid transition

Abstract

We present a set of measurements of the resistivity in Bi 2Sr 2CaCu 2O y as a function of the temperature T at fixed magnetic field H, ϱ H( T), and as a function of H at fixed T, ϱT( H), at different angles ϑ between H and the ( a,b) plane. In the ϱT( H) experiments an onset field for the resistivity H ☆ is detectable, and it has the same angular behavior as the upper critical field H c2 in traditional layered superconductors: H ☆ presents a round or cusp-like maximum when the magnetic field is directed close to the ( a,b) plane, depending on the temperature. H ☆ in perpendicular orientation is found to lie on the irreversibility line. Assuming that the irreversibility line is a critical field line for a glass-to-liquid transition, we show that a phenomenological model where the leading dissipative term is the phase slippage of the flux lines over a disordered network of inhomogeneities of the order parameter, with an activation process given by a Vogel-Fülcher equation, can fit all the data from low temperatures up to T c.