Orbital magnetization of a Mott insulator, V2O3, revealed by resonant x-ray Bragg diffraction

Structure factors calculated for x-ray Bragg diffraction by magnetically ordered vanadium sesquioxide, V 2 O 3 , with signal enhancement from the vanadium K-shell resonance, are compared with data gathered in azimuthal-angle scans at space-group forbidden reflections. Diffraction enhanced by a K-shell resonance reveals properties of the orbital magnetization in the valence shell of the resonant ion. whereas other core states, which have two partners because of the spin-orbit interaction, reveal properties of both the spin and orbital magnetization in the valence shell. Agreement on all issues between observed and calculated Bragg intensities support the use of an atomic model for the interpretation of data. The reflections are shown to be purely magnetic, and associated with the orbital magnetic moment and the octupole moment of a vanadium ion. Reflections with a Miller index h even are analyzed to give the canting angle of the magnetic easy axis. Data from the rotated (π'σ) and unrolated (σ'σ) channels of scattering provide an angle consistent with an earlier interpretation of magnetic neutron diffraction. With h odd, diffraction enhanced by an El event is forbidden. Intensities enhanced by an E2 event are from anisotropic components of the octupole moment. Analysis of azimuthal-angle scans, with h even and h odd, provides estimates of orbital moments that in the future can be confronted with ab initio calculations of the electronic properties of V 2 O 3 . By and large, the complicated pattern of azimuthal-angle scans can be attributed to the low symmetry (monoclinic) structure adopted below the Neel temperatures.