Chemical doping effect on the crystal structure and superconductivity of MgB2

Abstract

Substituent alloys of Mg1−xMxB2 with M=Ti, Zr, Mo, Mn, Fe, Ca, Al, Ag, Cu, Y, and Ho and 0x10% have been synthesized by the solid-state reaction. The solid solubility for most of these dopants at Mg site is found to be very low except for M=Al. In most of these alloys, the Vegard relationship holds as the doping level is low. The lattice constants for the fictitious compounds such as AgB2, CuB2, FeB2 have been extrapolated. The superconductivity transition temperature, Tc, shows a systematic changes with the doping level in some of these substituent alloys. Relevant mechanisms of superconductivity suppression have been discussed.