NATURE OF EXTRA-ATOMIC CORE-HOLE SCREENING IN FERROMAGNETIC NICKEL

Spin-resolved studies of Ni core-level photoemission are reported. The results indicate that the final-state Ni 3 d electron configuration in not purely 3d10, in contradiction with early theories emphasizing complete 3d-electron core-hole screening. A model is described in which extra-atomic screening involving unoccupied pure 3d states and unpolarized and hybridized 3d- 4sp states leads qualitatively to a final-state 3d valence configuration of 50% 3d9 and 50% 3d10. The relationship of these results to more recent theory employing the Anderson impurity model is discussed. © 1995 The American Physical Society.