Abstract
We investigated the possible origin of ferromagnetism due to a vacancy on a nonmagnetic ferroelectric PbTiO_3 surface by performing first-principles calculations within density-function theory. The results demonstrated that an oxygen vacancy intrinsically induced 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 originated from the spin-polarized d_<x2-y2> and d_<zx> states of the two Ti atoms nearest to the oxygen vacancy on the surface. The results presented here provide fundamental insights into the design of multiferroics in conventional ferroelectrics.
