Magnetism and half-metallicity at the O surfaces of ceramic oxides

The occurrence of spin polarization at ZrO2, Al2O3 and MgO surfaces is proved by means of ab initio calculations within the density functional theory. Large spin moments, as high as 1.56 mu(B), develop at O-ended polar terminations, transforming the non-magnetic insulator into a half-metal. The magnetic moments mainly reside in the surface oxygen atoms and their origin is related to the existence of 2p holes of well defined spin polarization at the valence band of the ionic oxide. The direct relation between magnetization and local loss of donor charge makes it possible to extend the magnetization mechanism beyond surface properties.