Electronic structure and origin of ferromagnetism in Ga_(1-x)Mn_xAs semiconductors

摘要

We perform a detailed theoretical study, within the density-functional theory, of the electronic structure and magnetic properties of Ga_(1-x)Mn_xAs diluted semiconductors. Ab initio total energy results provide evidence that the appearance of a ferromagnetic state in these materials is due to an exchange coupling between the localized ↑ S = 5/2 Mn spins mediated by quasi-localized ↓ holes, with strong p-like character, surrounding the fully polarized Mn d~5-electrons. From total energy differences, we find the effective Mn-Mn coupling always ferromagnetic, with the Mn-Mn interaction intermediated by an antiferromagnetic coupling of each Mn spin to the holes.