Atomic ordering, magnetic properties, and electronic structure of Mn2CoGa Heusler alloy

Abstract

The magnetic properties and atomic arrangement of Mn2CoGa Heusler alloy were investigated experimentally and by theoretical calculations. The magnetic moment derived from spontaneous magnetization at 5 K was 2.06 μB/f.u. and was close to the integer number of the expected value from theoretical calculation and the Slater–Pauling rule predicted by Galanakis et al. The Curie temperature and L21-B2 order–disorder phase transition temperature were 741 and 1047 K, respectively. Powder neutron diffraction experiment results suggested that the atomic arrangement prefers an L21b-type structure rather than that of Hg2CuTi, being consistent with our previous results of high-angle annular dark-field-scanning transmission electron microscopic observations. The magnetic moments obtained were in good agreement with the theoretical values in the model of the L21b-type structure. The density of states obtained by the first-principles calculation combined with the coherent potential approximation in Mn2CoGa with the L21b-type crystal structure maintained the half-metallic character, even though disordering by Mn and Co atoms was introduced.