PHOTOEMISSION WITH HIGH ANGULAR AND ENERGY RESOLUTION - TEMPERATURE-DEPENDENT EXCHANGE SPLITTING IN NICKEL

Ultraviolet photoemission spectroscopy data from a Ni(110) crystal taken with high angular and energy resolution at room temperature (RT) and near the ferromagnetic Curie temperature are presented. For a polar scan in the (001) plane we recorded energy spectra within 1.5 eV from the Fermi energy (E(F)) in 1 degrees steps. Distinct bands crossing EF can be well separated and, by comparing the RT data with a recent band structure calculation [H. Eckardt, L. Fritsche, J. Phys. F 17, 925 (1987)], the bands can be assigned to a minority d-band and two exchange split sp-bands. While their exchange splitting can hardly be extracted from the energy spectra, the peaks are well separated in k-space, i.e., in polar angle. We determine Delta E(ex) = 204 +/- 8 meV for the sp-band in the examined k-region and find that the angular line width of the majority sp-band is significantly smaller than that of the minority sp-band. Upon approaching T-C the exchange splitting of the sp-band vanishes and the d-band becomes very broad.