Vacancy-driven magnetism in nonmagnetic double perovskite Sr₂AlNbO₆: A first-principles study

Highlights: • Both Al and Nb vacancies could induce ferromagnetism in Sr₂AlNbO₆. • Ferromagnetism driven by Al vacancy originates from the 2p_x state of nearest O atoms. • Ferromagnetism induced by Nb vacancy comes from 2p_y and 2p_z states of nearest O atoms. • Sr₂AlNbO₆ with O vacancy is energetically more favorable than with others. - Abstract: Based on first-principles calculation the change of structural, energetic, magnetic and electronic properties of double perovskite oxide Sr₂AlNbO₆ is investigated by introducing intrinsic vacancies. Calculated results show that although both Al and Nb vacancies could induce ferromagnetism the nature of induced ferromagnetism is different. Ferromagnetism driven by Al vacancies originates from the remarkably spin-polarized 2p_x state of nearest O atoms, whereas that induced by Nb vacancy mainly comes from the partially filled spin-polarized 2p_y and 2p_z states of nearest O atoms. Sr₂AlNbO₆ with O vacancy is nonmagnetic but energetically more favorable than that with the other three vacancies