Para- to ferromagnetic phase transition of CoS₂ studied by high-resolution photoemission spectroscopy

We have performed temperature-dependent ultrahigh-resolution (ΔE∼7 meV) photoemission spectroscopy on CoS₂ across the para- to ferromagnetic transition and found a remarkable temperature-induced spectral change near E_F. Comparison With the band-structure calculation shows that a sharp peak at E_F in the photo-emission spectrum below Curie temperature (12 K) is ascribed to the e_g↓ subband due to the exchange splitting, indicating that the e_g↓ band is partially filled in the ferromagnetic phase. The present photoemission results indicate that the electronic structure and the magnetism of CoS₂ are qualitatively well described by the band-structure calculation although the correlation effect substantially modifies the electronic structure.