Global and local critical current density in superconducting SmFeAsO 1− xF x measured by two methods

Abstract

The critical current densities of polycrystalline bulk SmFeAsO 1− x F x prepared by the powder-in-tube (PIT) method and by a conventional solid-state reaction were investigated using the remnant magnetic moment method and Campbell’s method. Two types of shielding current, corresponding to global and local critical current densities J c were observed using both measurement methods. The global and local J c were on the order of 10 7 A/m 2 and 10 10 A/m 2 at 5 K, respectively. The local J c decreased slightly with increasing magnetic field. The global J c was independent of the preparation method, while the local J c was larger for samples prepared by PIT than for those prepared by solid-state reaction.