Temperature Dependence of the Exchange Splitting of the Surface State on Gd(0001): Evidence against Spin-Mixing Behavior

We report on angle-resolved photoemission (PE) and inverse PE studies of Gd(0001) in the temperature range 60 to 400 K. The results show that with increasing temperature both the occupied and the unoccupied parts of the d-like surface state at γ shift towards the Fermi level. This rules out a pure spin-mixing behavior as claimed recently on the basis of spin-resolved PE data. Instead, the temperature variation of the surface-state exchange splitting is Stoner-like, with an enhanced surface Curie temperature; nevertheless, a small residual splitting above TC cannot be ruled out.