Effect of Co addition on the critical current density of MgB2 superconductor

In this study, the (MgB2)1−xCox samples, where x=0.0, 0.1, 0.3, 0.6 and 0.8, were prepared by using the solid-state reaction technique. Effect of the Co-addition on the structural, magnetic, critical current density, Jc, and flux pinning properties of the superconducting MgB2 system was investigated. A magnetic transition was observed with increasing the Co-concentration in MgB2. For the pure MgB2, Jc was obtained to be 2.78×104 A cm−2 at 5 K and 1.7 kOe, but Jc was suppressed by addition of Co to the system. It was found that a large amount of Co in MgB2 did not act as pinning centers which improves Jc. The magnetic behavior observed by the Co-addition originates from the magnetic properties of cobalt itself.