TEMPERATURE-DEPENDENT CONDUCTION-BAND EXCHANGE SPLITTING IN FERROMAGNETIC HCP GADOLINIUM - THEORETICAL PREDICTIONS AND PHOTOEMISSION EXPERIMENTS

Angle-resolved photoemission is used to determine the temperature-dependent electronic properties of ferromagnetic bulk Gd along GAMMA-A of the three-dimensional Brillouin zone. The DELTA-2 band exchange splitting (0.85 eV) and dispersion (0.5 eV) are in reasonably good agreement with self-consistent local spin-density approximation calculations. The conduction-band magnetic exchange splitting vanishes at the Curie temperature following a conventional power law with a Heisenberg critical exponent. This "Stoner model" collapse of the exchange splitting is in striking contrast to corresponding results observed in transition-metal ferromagnets.