Polar Catastrophe, Orbital Reconstruction, and Emergent Ferromagnetic Exchange Coupling at the SrFeO2(001) Surface
文摘
The FeO2-terminated (001) surface of the stable antiferromagnetic insulating phase of the infinite-layer oxide SrFeO2 is found to undergo a magnetic reconstruction consisting of a spin-flip process at the surface: Each Fe spin at the surface flips to pair with one in the subsurface layer. In spite of the polar catastrophe inherent at the polar surface, the behavior is driven by a reduced intra-atomic 3dz2鈥?s hybridization and the enhanced Hund鈥檚 coupling due to surface symmetry lowering. These results, based on density-functional theory, show a surface-driven ferromagnetic exchange coupling in transition-metal oxides and provide an effective avenue to realize unusual electronic and magnetic properties.