Emergence of ferromagnetism at a vacancy on a non-magnetic ferroelectric PbTiO3 surface: A first-principles study

Abstract We investigated the origin of ferromagnetism due to a vacancy on a non-magnetic ferroelectric PbTiO 3 (0 0 1) surface using first-principles spin-density-functional theory calculations, and successfully provided electronic-level insights into this phenomenon. The results demonstrate that an oxygen vacancy intrinsically induces ferromagnetism, which is remarkably enhanced and stabilized on the TiO 2 -terminated surface favorably rather than inside PbTiO 3 . Detailed electronic structure analysis revealed that the ferromagnetism originates from the spin-polarized d zx and d x 2 - y 2 states of the two Ti atoms nearest to the oxygen vacancy on the surface. The origin of ferromagnetism for an oxygen vacancy inside PbTiO 3 differs from that an oxygen vacancy on the surface; it is due to the e g ( d x 2 - y 2 and d z 2 ) state of the single nearest Ti atom. These findings provide significant fundamental insights for designing multiferroics in conventional ferroelectrics.