Orbital topology, interlayer spin coupling, and magnetic anisotropy of the CuFeO2 compound

X-ray absorption spectroscopy performed on a CuFeO2 single crystal reveals the pivotal role of the Cu ions in the discussion of the anisotropic properties of the compound. In particular, it is shown that there is a 3d hole density on the nominal 3d(10) Cu+ ions which may lie at the origin of the intriguing low temperature magnetic properties of CuFeO2. In addition, the finding has important consequences regarding the field-induced ferroelectricity of the system.