Spin-resolved x-ray photoemission from ferromagnetic nickel.

Abstract

Spin-resolved x-ray photoelectron-spectroscopy (SRXPS) studies of metallic-Ni core-level and valence-band photoemission are reported. Prominent spin polarizations are observed for all main components and satellites. A spin-dependent splitting of 0.38 eV is observed for the main Ni 3s component. The Ni 3s 6-eV satellite, as well as a secondary satellite located \ensuremath{\sim}14 eV from the main 3s peak, both display a nearly 100% majority-spin polarization. Analogous results are found for the Ni 2s level. The 6- and 14-eV satellites are assigned to final states derived from the $^{1}$G and $^{1}$S states, respectively, of a local \ensuremath{\sim}3${\mathit{d}}^{8}$ final-state valence configuration that is created by the shakeup of a \ensuremath{\downarrow}-spin 3d electron to states above ${\mathit{E}}_{\mathit{f}}$. The manifestation of these phenomena in SRXPS studies of the Ni valence band, 3p, 2${\mathit{p}}_{3/2}$, and 2${\mathit{p}}_{1/2}$ core levels is presented and discussed. The SRXPS data are consistent with an itinerant-electron extra-atomic screening model in Ni involving both unoccupied pure 3d states and unoccupied, unpolarized, and hybridized 3d-4sp states. Final-state occupation of these states following photexcitation leads qualitatively to a final-state Ni 3d valence configuration of \ensuremath{\sim}50% 3${\mathit{d}}^{9}$ and \ensuremath{\sim}50% 3${\mathit{d}}^{10}$. The 3${\mathit{d}}^{9}$ configuration is the origin of the satellite production in Ni.