First-principles study of vacancy-induced ferromagnetism in nonmagnetic double perovskite Sr2AlTaO6

The changes of structural, energetic, magnetic and electronic properties in double perovskite oxide Sr2AlTaO6 due to introducing intrinsic vacancies are investigated by first-principles calculation. Calculated results show that although both Al and Ta vacancies could induce ferromagnetism the nature of induced ferromagnetism is different. Ferromagnetism driven by Al vacancy originates from the remarkably spin-polarized 2px state of nearest O atoms, whereas that induced by Ta vacancy mainly comes from the partially filled spin-polarized 2py and 2pz states of nearest O atoms. Sr2AlTaO6 with O vacancy is nonmagnetic but energetically more favorable than that with the other three vacancies.