Half-metallic properties and stability of ferromagnetic state in the full-Heusler alloys (FexRu1-x)(2)CrSi (0 <= x <= 1)

We investigate the half-metallic properties and the stability of the ferromagnetic state in the alloys (FexRu1-x)(2)CrSi (0 <= x <= 1) with orderly and disorderly atomic arrangement based on the Heusler structure. It is predicted from the electronic structures that the ordered alloys are half-metals in the range of 1/3 < x < 3/4 and ferromagnets with high spin polarization in the range of 3/4 < x < 1. However, in the ferromagnetic state, the atomic arrangement with the Fe-Cr disorder tends to be energetically more favorable than the orderly arrangement, and the Fe-Cr disorder decreases the spin polarization of the ordered alloys. This is attributed to the fact that occupation of Cr sites by Fe destroys the gap near the Fermi energy in the minority spin state. But, because the Fe-Cr disorder shows a tendency to keep the spin polarization high as x increases, it is deduced that (FexRu1-x)(2)CrSi are materials with high spin polarization if x is high.