Exchange interaction and ferromagnetism in III-V semiconductors

The mechanism of indirect exchange interaction leading to ferromagnetism in magnetically doped III-V semiconductors is considered theoretically. The mechanism is based on the interplay of two interactions: (i) hybridization of band states with shallow impurity ones, and (ii) direct exchange coupling between localized spins and the band states. The indirect exchange interaction between two Mn impurities occurs when the wave functions of shallow states associated with the Mn atoms overlap. The mechanism does not rely on degenerate carriers, and therefore can describe the ferromagnetic transition in both degenerate and nondegenerate semiconductors. Ferromagnetic critical temperature has been calculated within the percolation approach, and is in good agreement with available experimental data.