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

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 μ _B/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 L2_1b-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 L2_1b-type structure. The density of states obtained by the first-principles calculation combined with the coherent potential approximation in Mn₂CoGa with the L2_1b-type crystal structure maintained the half-metallic character, even though disordering by Mn and Co atoms was introduced.