X-Ray Resonant Scattering as a Direct Probe of Orbital Ordering in Transition-Metal Oxides

TL;DR

This paper demonstrates that X-ray resonant scattering at the K-edge can directly measure orbital order in transition-metal oxides, providing detailed insights into the orbital structure, especially in non-centrosymmetric cases like V$_2$O$_3$.

Contribution

It shows how X-ray resonant scattering can be used as a direct probe of orbital ordering, including the effects of symmetry and dipole contributions.

Findings

Resonant scattering measures orbital order parameters.

Dipole components enhance resonance in non-inversion symmetric cases.

Orbital structure in V$_2$O$_3$ is experimentally accessible.

Abstract

X-ray resonant scattering at the K-edge of transition metal oxides is shown to measure the orbital order parameter, supposed to accompany magnetic ordering in some cases. Virtual transitions to the 3d-orbitals are quadrupolar in general. In cases with no inversion symmetry, such as V$_2$O$_3$, treated in detail here, a dipole component enhances the resonance. Hence, we argue that the detailed structure of orbital order in V$_2$O$_3$ is experimentally accessible.