Effects of spin-orbit interaction in chromium on oxygen K-edge x-ray magnetic circular dichroism spectra in CrO2

We calculate the oxygen K-edge x-ray magnetic circular dichroism (XMCD) spectra of CrO2 to investigate the origin of light-element XMCD. The XMCD spectra evaluated by using a multiple scattering theory are interpreted in terms of the spin-orbit interaction (SOI) at each atomic site. We find that the SOI at the nearest-neighbor Cr atoms dominantly contributes to the oxygen K-edge XMCD. Since it has been speculated that XMCD originates from the spin polarization and the SOI at the x-ray-absorbing atom, the present finding may lead to modification of the previously speculated mechanism underlying K-edge XMCD. We also perform calculations with a small CrO2 cluster to examine how the O-p and Cr-d states are hybridized and how oxygen atoms acquire orbital angular momentum density. Strong K-edge XMCD features reflect the character of the d states of neighboring magnetic atoms and do not directly connect to the orbital magnetic moments of light-element p states.