Magnetic properties and electronic structure of the Heusler compounds Ru2-x Fex CrSi

We have been trying to find Heusler compounds with high spin polarization which are robust against chemical disorders, because it is considered that disorders often degrade high spin polarization. The Heusler compound Ru2-x Fe:cCrSi is shown to be such a material from first principles band structure calculations, and it is also shown that for the Ru-rich compound antiferromagnetic states are energetically preferable to the ferromagnetic state. Experimentally the Fe-rich compound is shown to be ferromagnetic, whereas for x ≤ 0.2 ferromagnetism is found to disappear and a cusp in the temperature dependence in magnetization is found, which appears to indicate an antiferromagnetic transition. These results seem to agree with the theory on the whole. The experimental results are examined in the light of calculated band structures.