Spin-polarized angle-resolved photoemission study of the electronic structure of Fe(100) as a function of temperature

By spin- and angle-resolved photoemission with synchrotron radiation the electronic structure of Fe(100) has been tested between room temperature and the Curie temperature ${T}_{C}$ for photon energies in the range 20\char21{}70 eV. The spin-resolved energy-distribution curves (SREDC's) reflect the dispersions of the ${\ensuremath{\Delta}}_{5}^{\ensuremath{\uparrow}}$,\ensuremath{\downarrow}-symmetry initial-state bands. This manifests in an abrupt change in spin character of the peak near ${E}_{F}$ from predominantly minority spin to majority spin when tuning the photon energy across 33 eV. The non-spin-resolved EDC's thereby remain nearly unchanged. Upon heating to 0.85T/${T}_{C}$, depending on photon energy, qualitative different changes in the SREDC's are observed: At h\ensuremath{\nu}=60 eV, ${\ensuremath{\Gamma}}_{25}^{\mathcal{'}\ensuremath{\uparrow}}$ is found to be stationary in energy upon heating, and the spin-summed intensity decreases by less than 5%. At ${\ensuremath{\Gamma}}_{25}^{\mathcal{'}\ensuremath{\downarrow}}$, a strong loss of intensity occurs. In contrast, at h\ensuremath{\nu}=31 and 21 eV, an increase in minority-spin (and total) photocurrent upon heating is observed. This is interpreted as resulting from a decrease of the exchange splitting with temperature near H.