Experimental determination of B-T phase diagram of YBa_2Cu_3O_7-d to 150T for B perpendicular to c

摘要

The B-T phase diagram for thin film YBa_2Cu_3O_7-d with B parallel to thesuperconducting layers has been constructed from GHz transport measurements to150T. Evidence for a transition from a high T regime dominated by orbitaleffects, to a low T regime where paramagnetic limiting drives the quenching ofsuperconductivity, is seen. Up to 110T the upper critical field is found to belinear in T and in remarkable agreement with extrapolation of the longstandingresult of Welp et al arising from magnetisation measurements to 6T. Beyond thisa departure from linear behaviour occurs at T=74K, where a 3D-2D crossover isexpected to occur.