Spin-dependent valence-band density of states of 3d ferromagnets

Spin-resolved X-ray photoelectron spectroscopy (SRXPS) and high resolution X-ray photoelectron spectroscopy (HRXPS) studies of the valence bands of ferromagnetic Fe, Co, Co₆₆Fe₄Ni₁B₁₄Si₁₅ and Ni are reported. The SRXPS and HRXPS spectra are compared with theoretical densities of states (DOS) that are corrected for photoelectric cross section variations within the valence band. Agreement between theory and experiment is very good for ferromagnetic Fe and Co₆₆Fe₄Ni₁B₁₄Si₁₅. For Co metal, experiment agrees poorly with theory incorporating a 1.5 eV exchange splitting. Agreement is improved if a reduced Co exchange splitting of 1.2 eV is adopted theoretically. The reduced exchange splitting is attributed to valence electron correlation in Co metal. Ferromagnetic Ni shows poor agreement between experiment and theory. The SRXPS Ni spectra demonstrate that most of the disagreement concerns the ↑-spin channel.