Control of magnetic properties in Fe doped and (Fe, Ni) codoped InN by nonmagnetic substitution

Abstract

First-principle calculations have been performed to investigate electronic structures and magnetic properties of Fe doped and (Fe, Ni) codoped InN within the generalized gradient approximation + U and plane-wave ultra-pseudopotential schemes. The results demonstrate that the formation energy of Fe doped and (Fe, Ni) codoped InN is negative and the doped systems have better stability. It is found that the Fe doped InN with nonmagnetic Si substitution and the (Fe, Ni) codoped InN with nonmagnetic Mg substitution present more stable ferromagnetic coupling. It is suggested that the ferromagnetism of the systems may be derived from the magnetic exchange interaction between the host band and the down-spin electronic states in the bandgap. It is worth noting that due to p-d hybridization, the introduction of Mg atoms into the (Fe, Ni) codoped InN and that of Si atoms into Fe-doped InN cause the spin electron states in the valence band to further expand into the bandgap and approach the down-spin electronic states in the bandgap. This may enhance the ferromagnetic stability and enable the systems to obtain high temperature ferromagnetism. In addition, the existence of N vacancies enhances the ferromagnetic coupling of (Fe, Ni) codoped InN system, and may be used to increase the Curie temperature of the doped system. The presented results support the potential of synthesizing p-type and n-type InN-based magnetic semiconductors by the appropriate selection of transition metals (TM) co-doped with nonmagnetic atoms.