Orbital magnetic moments of CoO and FeO and isotropic Co and Fe L2,3 absorption spectroscopy

The relationship between the magnetic state of divalent Co and Fe ions in the octahedral crystal field and the isotropic L-2,L-3 X-ray absorption spectroscopy (XAS) spectrum is discussed with switching on and off the 3d spin-orbit interaction on the basis of an atomic multiplet calculation. The existence of orbital magnetic moment M-orb of similar to 1 mu(B) is shown to manifest especially in L-2 region as a narrow spectrum compared with that for M-orb = 0 for both ions. A deviation of L-3 : L-2 braching ratio from the statistical ratio 2 is also shown to be closely related with the existence of M-orb for both ions. In the light of our findings, the magnetic state of both ions in CoO and FeO is discussed. The role of isotropic core XAS as a means to determine M-orb in systems with no net magnetization is stressed.