First-principles study for vacancy-induced magnetism in nonmagnetic ferroelectric BaTiO3

The possibilities of vacancy-induced magnetism in perovskite BaTiO3 are investigated by first-principles calculations. Calculated results show that both titanium and oxygen vacancies could induce magnetism, but the barium vacancy did not induce magnetism. New and interesting magnetic properties of half-metallic magnetism are found in BaTiO3 induced by the Ti-vacancy. Based on the density of states and the spin charge density distribution of BaTiO3, we discuss the different origins of magnetism induced by the partial spin-polarized O 2p states around Ti vacancies and the partially filled d-states Ti around the oxygen vacancies. The discrepancy between the magnetic moments in the cubic phase and the tetragonal phase is due to anisotropic spin polarization induced by structure distortions. Our calculations would enable exploring magneto-electric coupling in nonmagnetic ferroelectric oxides.