Surface Segregation and Compositional Instability at the Surface of Half-Metal Ferromagnets and Related Compounds

Abstract

Interface engineering in order to exploit the possibilities of the interface electronic structure may be a route to a good spin injector. Nonetheless, for many potential half metallic systems, the stoichiometric surface is generally not in thermodynamic equilibrium with the bulk and the surface Debye temperature is often quite low. Several such classes of materials are currently under investigation as potential high spin polarization materials. These include the half metallic systems such as the semi-Heusler alloys, the manganese perovskites and the simpler oxides like chromium dioxide and magnetite. But all these materials suffer from a tendency of the surface to adopt a different composition than the bulk. Surface segregation and surface composition for three classes of potential half metallic systems: NiMnSb(100), La 0 . 6 5 (M=Ca,Pb,Sr) 0 . 3 5 MnO 3 (100) and CrO 2 will be explored. The surface compositional stability and different surface terminations will be compared with the results from recent electronic structure calculations.