Stability of Half-Metallic Ferromagnetism of Zinc-Blende Type CrAs and MnM(M=Si, Ge and Sn)

By the first-principles calculations both for electronic structures and effective exchange constants, we investigate the stability of ferromagnetism of zinc-blende (ZB) type CrAs, and further examine a possibility of ferromagnetism of ZB type Mn M ( M =Si, Ge and Sn). ZB type CrAs, a half-metallic ferromagnet reported by Akinaga's group [Jpn. J. Appl. Phys. 39 (2000) L1118], is found to have an effective exchange constant ( J 0 =∑ i ≠0 J i 0 ) larger than 150 meV above the lattice constant of GaAs ( a =5.65 Å), showing quite stable ferromagnetism above room temperature as was observed experimentally. We predict that ZB type Mn M ( M =Ge, Si, Sn) whose valence electron numbers are the same as that of CrAs also exhibit half-metallic ferromagnetism having a positive J 0 large enough at a =5.82 Å, indicating that the Curie temperatures are higher at least than room temperature.