Magnetic states at the oxygen surfaces of ZnO and Co-doped ZnO.
First principles calculations of the O surfaces of Co-ZnO show that substitutional Co ions develop large magnetic moments which long-range order depends on their mutual distance. The local spin polarization induced at the O atoms is 3 times larger at the surface than in the bulk, and the surface stability is considerably reinforced by Co. Moreover, a robust ferromagnetic state is predicted at the O (0001) surface even in the absence of magnetic atoms, correlated with the number of p holes in the valence band of the oxide, and with a highly anisotropic distribution of the magnetic charge even in the absence of spin-orbit coupling.
Sanchez
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Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid 28049, Spain.
Gallego
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Muñoz
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MC