GROUND-STATE OF FERROMAGNETIC NICKEL AND MAGNETIC CIRCULAR-DICHROISM IN NI 2P CORE X-RAY-ABSORPTION SPECTROSCOPY

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 3d10, 3d9, and 3d8 configurations with relative weights of 15%-20%, 60%-70%, and 15%-20%, respectively, and with an orbital-magnetic-moment contribution of approximately 0.07-mu-B to the total moment of 0.6-mu-B. With these results, we can explain the recently observed MCD in Ni 2p XAS.