Recently, new compounds Mn 2 RuSn and Mn 2 RuSi were synthesized and their crystal structures were studied by X-ray diffraction measurements. This measurement indicates that they have a Heusler-like cubic structure, but the details have been unclear so far. To clarify their atomic arrangement and magnetic order, we carried out first-principles total-energy calculations for several different atomic arrangements, together with ferrimagnetic and ferromagnetic ordering. The comparison among total energies indicates that the most stable structure is a ferrimagnetic Hg 2 CuTi one in both Mn 2 RuSn and Mn 2 RuSi. We also found that the compound Mn 2 RuSi with the Hg 2 CuTi structure could be a half-metallic ferrimagnet.

Recently, new compounds Mn 2 RuSn and Mn 2 RuSi were synthesized and their crystal structures were studied by X ray diffraction measurements. The measurements showed that they have a Heusler like cubic structure, but the details have been unclear so far. Therefore, to clarify their atomic and magnetic order, we have carried out first principles total energy calculations for several different atomic arrangements, together with ferrimagnetic and ferromagnetic orders. The comparison among total energies shows that the most stable structure is ferrimagnetic Hg 2 CuTi one in both Mn 2 RuSn and Mn 2 RuSi. It is also found that the compound Mn 2 RuSi with a Hg 2 CuTi structure could be a half metallic ferrimagnet.