Vacancy-induced magnetism in ferroelectric LiNbO3 and LiTaO3

Abstract The possibilities of d 0 magnetism induced by various defects in ferroelectric LiTaO 3 and LiNbO 3 are investigated by ab initio calculations. The stoichiometric LiTaO 3 and LiNbO 3 are nonmagnetic. The neutral Li, Nb and Ta vacancies could induce magnetism in LiNbO 3 and LiTaO 3 , due to the spin-polarization of O 2p electrons. The neutral O vacancy could bring about the magnetic moment in LiNbO 3 , due to the spin-polarization of Nb s electron at the impurity band. For LiNbO 3 and LiTaO 3 with two neutral Li, Nb and Ta vacancies, ferromagnetic coupling are found to be energetically more favorable than antiferromagnetic coupling, except when two neutral Ta vacancies are 1st nearest-neighbored. For LiNbO 3 with two neutral O vacancies, the antiferromagnetic coupling is preferred when two neutral O vacancies are 1st and 2nd nearest-neighbored, and the ferromagnetic coupling is energetically favorable when two neutral O vacancies are 3rd nearest-neighbored. It is possible to obtain the d 0 LiNbO 3 and LiTaO 3 multiferroic materials through the introduction of appropriate intrinsic vacancies in them.