Ab initio study of ferromagnetic semiconductor Ge_1-xMn _xTe

First-principles calculations are made on the Ge_1-xMn _xTe diluted magnetic semiconductors with different compositions. The origin of their ferromagnetism is investigated and the carrier-induced ferromagnetism is developed for these diluted magnetic semiconductors. The Mn 3dstates localized with divalent character are deep below the Fermi level, and the carriers introduced by defects are supported in our calculation. The pstates of Ge also play an important role in the occurrence of ferromagnetism especially at high temperature. It is thought that Ge_1-xMn _xTe with a moderate composition (x ≤ 0.51) of Mn atoms is a good candidate for DMS materials.