Microscopic origin of ferromagnetism in Fe-doped III-V semiconductors

Recently, Fe-doped III-V type semiconductors have attracted much attention due to the following two reasons. (i) (In,Fe)Sb and (Ga,Fe)Sb possess the room temperature ferromagnetism. (ii) although the ferromagnetism in general DMS systems originates from p-type carriers, (In,Fe)As and (In,Fe)Sb show electron-induced ferromagnetism. However, the microscopic mechanisms of such high Curie temperature and electron-induced ferromagnetism are still not clear. To understand the origin of such novel magnetic properties, we investigate the electronic structure, magnetic properties, and structural stabilities in the Fe-doped III-V semiconductors by the Korringa-Kohn-Rostoker (KKR) Green's function method within the density functional theory. It is found, from our calculations, that the intrinsic Fe-doped III-V semiconductors have strong antiferromagnetic interaction due to the super-exchange mechanism. By both n- and p-type dopings, i.e. changing the Fermi energy, we can drastically change the magnetic states from the antiferromagnetic to ferromagnetic ordering. This magnetic transition can be well understood by the Alexander-Anderson-Moriya mechanism. On the basis of our calculations, we also propose a new method for the control of magnetization by electric field (gate voltage).