On the propensity of magnetism in 3d transition-metal-MgCNi3 alloys

Abstract

The effects of disorder and incipient magnetism in MgCðNi 1Àx T x Þ 3 (T Fe, Co or Cu) alloys are studied using coherent-potential approximation and Ginzburg-Landau coefficients. The first-principles, local-density-functional-based calculations for substitutionally disordered Fe and Co impurities in the Ni sub-lattice of MgCNi 3 , in low concentrations, show that incipient magnetism resides in these materials. The overestimation of the calculated magnetic properties points to the limitations of the local-density approximation. However, using a phenomenological approach based on Ginzburg-Landau coefficients and the fixed-spin moment method, we show that MgCðNi 1Àx T x Þ 3 alloys remain paramagnetic. At expanded volumes, we also find the possibility of a ferromagnetic state for MgCðNi 0:95 Fe 0:05 Þ 3 and MgCðNi 0:90 Co 0:10 Þ 3 alloys. r