Temperature and Magnetic Field Dependence of the Critical Current in Polycrystalline Ba2YCu3Oy

Abstract
The temperature and magnetic field dependence on the critical current density, J c, of the polycrystalline Ba2YCu3O y have been measured. In the low magnetic field range, 0.6∼7 kOe, the J c behavior changed at around 70 K. Below 70 K, J c showed different temperature dependences between field cooling and zero-field cooling, that is, the J c value measured when the sample was cooled in a fixed magnetic field was different from that measured when the sample was cooled in zero magnetic field and then a magnetic field was applied. Above 70 K, however, such different temperature dependences on J c were not observed. These experimental results can be attributed to the effects of anisotropy, and a crossover between two- and three-dimensional superconductivity is considered to occur.