Carrier Mediated Ferromagnetism in Fe-doped SrTiO$_{3}$

The discovery of III-V dilute magnetic semiconductors (DMSs) and the subsequent unsuccessful search for room temperature ferromagnetism in DMSs have motivated researches on alternate dilute magnetic systems. Recent progresses in thin flim growth techniques of perovskite oxides suggest that dilute magnetic oxides (DMOs) can be viable candidates to improve the magnetic properties of DMSs. In this talk we present an ab initio study of Fe-doped SrTiO$_{3}$. We find that a ferromagnetic ordering among localized Fe t$_{2g}$~spins is mediated by itinerant Fe e$_{g}$~electrons. The exchange interaction between t$_{2g}$~and e$_{g}$~electrons depends on crystal field splitting, on-site electron-electron interaction, and the relative energy of Fe d-ortbitals to oxygen p-orbitals. The exchange coupling and the majority-minority spin splitting decrease with decreasing carrier concentration, confirming that itinerant carriers mediate the ferromagnetism.