EXPERIMENTAL ENERGY-BAND DISPERSIONS AND EXCHANGE SPLITTING FOR NI

Angle-resolved polarization-dependent photoelectron spectroscopy using synchrotron radiation has been used to determine the energy-versus-momentum band dispersions and magnetic exchange splitting of Ni. Using Ni(111) and Ni(100) crystals, the band dispersions along the Γ-L and Γ-X lines have been determined for the s and d bands. The temperature-dependent magnetic exchange splitting ΔEex of the upper Λ3 band has been directly observed and found to be independent of momentum k→ for a large region of the Brillouin zone. The experimental value of ΔEex=0.31±0.03 eV is smaller than recent calculated values (0.6≤ΔEex≤0.9 eV) obtained with spin-polarized self-consistent band calculations. Also, calculated d-band widths are larger (typically 40%) than measured (3.4 eV at L). Our results are consistent with Fermi-surface data and the polarization reversal observed in spin-polarized photoemission. A number of previous contradictory photoemission studies of Ni are discussed in view of our results. The observed bands show that ferromagnetic nickel can be described by a Stoner-Wohlfarth-Slater spin-split band model. © 1979 The American Physical Society.