X-ray magnetic circular dichroism sum rule correction for the light transition metals

Abstract

Distinguishable L2 and L3 edges and a clear separation into j 3/2 and j 1/2 excitations are necessary for the application of L2,3 edge X-ray magnetic circular dichroism (XMCD) sum rules, which provide element-specific information about spin and orbital magnetic moments. This separation is present for the heavy transition metals (TM), like Co and Ni, due to their large L2,3 spin–orbit splitting. However, for the light TM, the 2p spin–orbit splitting is strongly reduced and quantum mechanical mixing of j 3/2 and j 1/2 excitations is present. This mixing reduces the observed XMCD related spin and magnetic dipole term contributions and prevents the direct application of XMCD spin sum rules. A large number of 2p → 3d absorption spectra have been fitted nearly perfectly by a simple and phenomenological model, which takes into account lifetime effects and provides quantitative information about jj-mixing at the light TMs. On the basis of this mixing coefficient, sum rule correction factors have been determined. The proposed model results in renormalized magnetic projected XMCD spin moments, verified for different compounds of V, Cr, and Mn. A comparison with complementary methods gives consistent results. This or a similar fitting procedure and the estimated correction factors can be used in the future as a light element XMCD spin renormalization technique.