Critical current density and flux pinning in Ho-doped melt-processed YBa2Cu3Oy

Abstract

We fabricated highly textured Y1−xHoxBa2Cu3Oy (x=0, 0.2, 0.4, and 0.6) bulk samples by a ‘‘powder melting process’’ method under identical conditions and investigated their critical current densities and flux pinning behavior with a superconducting quantum interference device magnetometer. The dependence of Jc on the magnetic field, estimated by the Bean model, is studied. The results indicate that Jc drops with the magnetic field according to a power law Jc∝H−n (n<0.5), which implies that the Jc value of these samples is controlled by the flux pinning rather weak links. It is found that Jc and flux pinning can be significantly improved by Ho substitution for Y in Y-based superconductors. The reduction of the size of Y2BaCuO5 particles, stress-field pinning, and magnetic pinning created by the Ho addition are considered to be responsible for the increase in Jc and flux pinning.