Soft x-ray spectroscopic study of the ferromagnetic insulator V _0.82 Cr_0.18 O₂

The chromium-vanadium oxide system V_1-x Cr_x O ₂ (0.1<x<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_3,2, OK, and Cr L_3,2 edges was used to study the electronic structure near the Fermi level of V_0.82 Cr_0.12 O₂. Our results show that the chromium enters as Cr3⊃+ with the d3 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 Cr3d orbital is located ∼2 eV below the Fermi level. Comparison with the parent material VO₂ reveals significant changes in the O2p bandwidth and increased O2p-V3d hybridization in V_0.82 Cr_0.12 O ₂, 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 L₃ -edge x-ray scattering spectra and are explained in terms of the splitting of the t_2g -derived π band.