Soft x-ray spectroscopic study of the ferromagnetic insulator V0.82Cr0.18O2

The chromium-vanadium oxide system V1-xCrxO2 (0.1<0.2) displays both insulating character in the rutile phase and room-temperature ferromagnetism. A combination of x-ray photoemission spectroscopy, resonant inelastic x-ray scattering, and resonant x-ray emission spectroscopy of the V L-3,L-2, O K, and Cr L-3,L-2 edges was used to study the electronic structure near the Fermi level of V0.82Cr0.12O2. Our results show that the chromium enters as Cr3+ with the d(3) configuration, resulting in the formation of Cr3+-V5+ ion pairs, in contrast to the simple Cr4+ substitution expected from the end members VO2 and CrO2. The occupied Cr 3d orbital is located similar to 2 eV below the Fermi level. Comparison with the parent material VO2 reveals significant changes in the O 2p bandwidth and increased O 2p-V 3d hybridization in V0.82Cr0.12O2, which are attributed to the reduced atomic spacing upon doping. Two energy loss features due to d-d* transitions are observed at 0.95 and 1.75 eV in the V L-3-edge x-ray scattering spectra and are explained in terms of the splitting of the t(2g)-derived pi band.