Ground state of ferromagnetic nickel and magnetic circular dichroism in Ni 2pcore x-ray-absorption spectroscopy

Abstract

The electronic state of ferromagnetic Ni and the expected magnetic circular dichroism (MCD) in Ni 2p→3d x-ray-absorption spectroscopy [2p (XAS)] are discussed from a viewpoint of 3d configuration interaction on the basis of the Anderson impurity model. The model includes multiplet effects arising from 3d-3d and 3d-2p electron interactions and a 3d interatomic exchange approximated by a molecular field acting on the 3d spin. By using commonly accepted values of the interaction strengths, it is shown that the ground state of a Ni atom in ferromagnetic Ni is expressed by a superposition of 3${\mathit{d}}^{10}$, 3${\mathit{d}}^9$, and 3${\mathit{d}}^8$ configurations with relative weights of 15%–20%, 60%–70%, and 15%–20%, respectively, and with an orbital-magnetic-moment contribution of ∼0.07${\mathrm{\mu }}_{\mathit{B}}$ to the total moment of 0.6${\mathrm{\mu }}_{\mathit{B}}$. With these results, we can explain the recently observed MCD in Ni 2p XAS.