Ferromagnetism in IV main group element (C) and transition metal (Mn) doped MgO: A density functional perspective

The formation of magnetic moment due to the dopants with p-orbital (d-orbital) is named d0 (d −) magnetism, where the ion without (with) partially filled d states is found to be responsible for the observed magnetic properties. To study the origin of magnetism at a fundamental electronic level in such materials, as a representative case, we theoretically investigate ferromagnetism in MgO doped with transition metal (Mn) and non-metal (C). The generalized gradient approximation based first-principles calculations are used to investigate substitutional doping of metal (Mn) and non-metal (C), both with and without the presence of neighboring oxygen vacancy sites. Furthermore, the case of co-doping of (Mn, C) in MgO system is also investigated. It is observed that the oxygen vacancies do not play a role in tuning the ferromagnetism in presence of Mn dopants, but have a significant influence on total magnetism of the C doped system. In fact, we find that in MgO the d0 magnetism through C doping is curtailed by pairing of the substitutional dopant with naturally occurring O vacancies. On the other hand, in case of (Mn, C) co-doped MgO the strong hybridization between the C (2p) and the Mn(3d) states suggests that co-doping is a promising approach to enhance the ferromagnetic coupling between the nearest-neighboring dopant and host atoms. Therefore, (Mn,C) co-doped MgO is expected to be a ferromagnetic semiconductor with long ranged ferromagnetism and high Curie temperature.