Resonant Photoemission in Open and Closed 3d Shell Systems: Ni_xSi (x=3, 2.5, 2, 1.5, 1, and 0.5)

Abstract

Valence band photoemission spectra of six kinds of Ni_xSi (x=3, 2.5, 2, 1.5, 1, and 0.5) were measured with synchrotron radiation at photon energies around the Ni 3p core excitation threshold. The resonance in the Ni 3d band shows two minimum structures in the photon energy dependence of the peak height with a separation of 1.7 eV, which corresponds to the spin orbit splitting in the final state of Ni 3p core emission. Strong resonance at valence band satellite and main 3d band is found in Ni-rich compounds and the behavior of the resonance changes from Ni-like to Cu-like with decreasing x. These changes are interpreted by a rigid band model, in which the partially empty d band becomes to be fully occupied with decreasing x.