Temperature Dependence of the Exchange Splitting in Ni Studied by Spin-Polarized Photoemission

Angle- and spin-resolved photoemission spectra from Ni(110) have been measured in the temperature range $0.5<~\frac{T}{T_C}<~0.94$. The data cannot be reconciled either with the predictions of local band theory assuming a temperature-independent exchange splitting or with a pure Stoner model. It is concluded that the exchange splitting decreases with increasing temperature and that spin fluctuations strongly influence the photoemission line shapes.