Iron doping effect on superconducting properties of MgB2

Iron-doped MgB2 bulks are prepared by hybridized diffusion method using nano-powder and macro-powder of pure iron as iron source. The doping effect on superconductivity transition temperature, Tc, and critical current Jc have been investigated. It is found that both Tc and Jc of MgB2 show quite different features depending on the particle size of the dopant powders. It is demonstrated that different from iron bulk or large size powders, iron nano-powders are active dopant for MgB2 which suppresses both Tc and Jc of MgB2.