M. Giura et al., MAGNETORESISTIVITY MEASUREMENTS IN HTC SUPERCONDUCTORS - LAYERED BEHAVIOR AND VORTEX-GLASS-TO-LIQUID TRANSITION, Physica. C, Superconductivity, 209(1-3), 1993, pp. 341-344
We present a set of measurements of the resistivity in Bi2Sr2CaCu2Oy a
s a function of the temperature T at fixed magnetic field H, rho(H)(7)
, and as a function of H at fixed T, rho(T)(H), at different angles th
eta between H and the (a,b) plane. In the rho(T)(H) experiments an ons
et field for the resistivity H is detectable, and it has the same ang
ular behavior as the upper critical field H(c2) in traditional layered
superconductors: H presents a round or cusp-like maximum when the ma
gnetic field is directed close to the (a,b) plane, depending on the te
mperature. H in perpendicular orientation is found to lie on the irre
versibility line. Assuming that the irreversibility line is a critical
field line for a glass-to-liquid transition, we show that a phenomeno
logical 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-Fulcher
equation, can fit all the data from low temperatures up to T(c).