High-field magnetisation and the critical current density in superconducting BiSrCaCu2Ox

Abstract

Samples of notional composition BiSrCaCu2Ox have been prepared and shown to have a majority phase with lattice parameters a=5.395(3) AA, b=5.406(5) AA and c=30.84(1) AA which is superconducting below 80 K. Both the low-field DC magnetisation and resistivity indicate the presence of a minority superconducting phase with Tc>100 K. The intragrain critical current density Jc inferred from high-field magnetisation measurements on powder samples is estimated to be 5*105 A cm-2 at 4.2 K and 1 T, which is similar to that observed in YBa2Cu3O7. The form of the temperature and field dependence of Jc is also similar to that observed in YBa2Cu3O7. However, relaxation effects in the magnetisation are more pronounced, which is indicative of smaller flux pinning especially at high temperatures.