Reconstruction of the electronic structure in half-metallicCoS2

Temperature variation of reflectivity spectra (0.6--5.0 eV) has been investigated for ferromagnetic ${\mathrm{CoS}}_{2}.$ We have found significant spectral changes at the ferromagnetic transition ${(T}_{\mathrm{C}}=120\mathrm{}\mathrm{K}):$ (1) oscillator strength of the lower-lying interband transition $(\ensuremath{\sim}1.6\mathrm{eV})$ is suppressed, and (2) the higher-lying transition $(\ensuremath{\sim}3.4\mathrm{eV})$ shifts to the low energy side. We have ascribed the spectral change to the splitting of the ${e}_{g}$ state into the up-${(e}_{g\ensuremath{\uparrow}})$ and down-spin ${(e}_{g\ensuremath{\downarrow}})$ states, or the half-metallic behavior of ${\mathrm{CoS}}_{2}.$