Orbital and bonding anisotropy in a half-filled GaFeO3 magnetoelectric ferrimagnet -: art. no. 047205

We investigated the orbital anisotropy of GaFeO3 using the Fe L-2,L-3-edge x-ray magnetic circular dichroism and the polarization dependent O K-edge x-ray absorption spectroscopy. We found that the system shows a considerably large orbital momentum and anisotropic Fe-O bonding, which are unexpected in a half-filled d(5) system such as GaFeO3. The orbital and bonding anisotropies, which turn out to be induced by the lattice distortions with exotic off-centering site movements, contribute the large magnetocrystalline energy and magnetoelasticity. These results provide critical clues on the microscopic understanding of the magnetoelectricity.