Chemical Substitution Effect on MgB2Superconductor

Effects of chemical substitution on the superconductivity have been investigated in MgB 2 superconductor. Substitution of the Mn 2+ and Co 2+ ions for the Mg 2+ ions significantly suppresses the transition temperature T c at a rate of d T c /d x =-183 and -83 K. respectively. These doping effects are ascribed to the interaction between the local spin S and the constituent electron s of the Cooper pair.