Mean-field approach to ferromagnetism in (III,Mn)V diluted magnetic semiconductors at low carrier densities

摘要

We present a detailed study, within the mean-field approximation, of animpurity band model for III-V diluted magnetic semiconductors. Such a modelshould be relevant at low carrier densities, below and near the metal-insulatortransition. Positional disorder of the magnetic impurities inside the hostsemiconductor is shown to have observable consequences for the shape of themagnetization curve. Below the critical temperature the magnetization isspatially inhomogeneous, leading to very unusual temperature dependence of theaverage magnetization as well as specific heat. Disorder is also found toenhance the ferromagnetic transition temperature. Unusual spin and chargetransport is implied.