The superconductivity and metal-insulator transition in the Mg doped LaSrCuO system

Abstract Structure analysis, dc resistivity and ac susceptibility measurements on the Mg doped La 2−y Sr y Cu 1−x Mg x O 4 system were performed. It is observed that with the increase of Mg content x the superconducting (SC) transition temperature T c drops linearly to below 4.2 K, for Mg content greater than a critical concentration x c = 0.03 all the samples of the La 1.85 Sr 0.15 Cu 1- x Mg x O 4 system become semiconducting at low temperature, i.e. the metal-insulator (MI) transition occurs when varying the Mg content x in such a system across the critical content x c . Furthermore, such SC and MI transitions can be tuned by varying the Sr concentration y . These results have been explained by using a simple model based on the disorder induced localization effect.