Trapping Magnetic Field in Bulk Iron-based Superconductor Sintered under High Pressure

Abstract

We fabricated two bulk superconductors of (Ba,Na)Fe2As2 using a cubic press and hot press sintering technique. For bulk #1 sintered by cubic press, despite its small dimensions, with diameter 4.1 mm and height 3.64 mm, a trapped field value of ~9.97 kG has been achieved on its surface, which is only 230 G lower than the value reported in a bulk with a diameter of 10 mm before. Critical current density (J c) is estimated to be 81.2 kA cm−2 at 4.2 K under self-field, which is larger than the value reported before. It suggests that the improvement of J c achieved by high pressure could make up for the negative influence from the smaller dimensions and achieve a large trapped field. In the second larger bulk #2 sintered by hot pressing technique, with diameter 9.45 mm and height 4.58 mm, the value of J c is ~ 33.9 kA cm−2 and the trapped field is ~8.81 kG on the surface. The expected better texturing has not been observed. Possible origins for inferior properties of bulk #2 are discussed.