Defect-induced magnetism: Codoping and a prescription for enhanced magnetism

Recent works have given indication that the defect-induced magnetism in diluted magnetic semiconductors (DMSs), transition metal oxides (TMOs), and related materials is facilitated and enhanced by codoping and the synergistic action among the codopants. In the present work we demonstrate that the proposed defect-induced ferromagnetic coupling (FMC) exhibits the following features: bipartition, synergy, and locality, and is based on the formation and interaction among spin-polarized neighborhoods analogous to spin-polarized radicals centered at the codopant sites. The FMC is mediated by the molecular orbitals (MOs) of these radicals and is greatly facilitated if the codopant-centered radicals could form bipartite configurations within the host lattices. Within this picture, the origin of magnetism in DMSs and TMOs appears to be the synergy and the interplay between correlated spin-polarization processes that take place in a successive way within neighborhoods centered at the codopants and include their first nearest neighbors (1nns). The proposed model can be used as a practical guide for choosing the appropriate pair of codopants for a specific semiconductor environment that can lead to the fabrication of DMSs and TMOs with enhanced magnetic properties.