Effect of Ir-addition on Pinning Property of MgB2

The 5d transition metal Ir was added into the MgB2 superconductor. The Mg, B and Ir were sintered at 1173K for 30 minutes under Ar-H2 atmosphere in the electric furnace. The nominal Irx(MgB2)1-x samples were prepared in the Ir concentration range of 0 < x< 0.05. Electrical resistivity ρ was measured between 20K and 50K by the 4-terminals method. The field and x-dependence of Jc at 20K were analyzed by the extended critical state model. The enhancement of Jc was observed for the x = 0.01 sample.