Study of Upper critical magnetic field of ( 0.8Pr 0.2)Ba 2Cu 3O 7-σ thin film

Abstract

Measurement of the current-voltage characteristics of (Y 0.8Pr 0.2Ba 2Cu 3O 7−σ thin film near S-N transition has been carried out systematically. Temperature dependence of the upper critical field H c2 of the film was then derived according to a model based on the Bardeen-Stephen theory. The resulted H c2 ( T) curves show clear positive curvature, similar to that derived from temperature dependence of resistance of YBa 2(Cu 0.97Zn 0.03)O 7−σ thin films, La 2–xSr xCuO 4 and Tl 2Ba 2CuO 7−σ single crystals. Measurements of temperature dependence of resistivity of the same sample at magnetic fields up to 7 Tesla were also carried out and the resulted upper critical field H c2 ( T) curves are compared with those derived from current-voltage characteristics.