Full-potential screened KKR calculations for magnetism of Co 2MnSi, Ni2MnAl and Ru2MnSi, based on the generalized gradient approximation

Abstract

We present systematic ab-initio calculations for nonmagnetic (NM), ferromagnetic (FM), and antiferromagnetic (AFM) states of full-Heusler alloys (X2YZ) such as Co2MnSi (X = Co, Y = Mn, Z = Si), Ni 2MnAl (X = Ni, Y = Mn, Z = Al), and Ru2MnSi (X = Ru, Y = Mn, Z = Si). The calculations are based on the all-electron full-potential (FP) screened Korringa-Kohn-Rostoker (KKR) Green's-function method combined with the generalized-gradient approximation in the density-functional formalism. We show that the present calculations reproduce very well the experimental ground states of these alloys (FM of Co2MnSi and Ni2MnAl, AFM of Ru2MnSi) and the available measured values for lattice parameters and magnetic moments. It is also shown that the fundamental features of the magnetism of Co2MnSi (strong FM) and Ni2MnAl (weak FM) are understood by using the Mn spin-flip energies and the Mn-Mn exchange interaction energies in X (= Co, Ni), both of which are obtained by the present FP-KKR calculations for the impurity systems. We can show that the magnetism of Ni2MnAl may be changed from FM to AFM by atomic disorder (B2-structure) occurring at elevated temperatures. © 2008 The Japan Institute of Metals.