Half-metallic density of states in ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ due to Hund’s rule coupling

We have investigated the electronic structure of ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ by photoemission spectroscopy and band-structure calculations within the local-density $\mathrm{approximation}+U$ $(\mathrm{LDA}+U)$ scheme. In valence-band photoemission spectra, a distinct double-peak feature has been observed near the Fermi level ${(E}_F).\mathrm{}$ A photon-energy dependence of the spectra and the $\mathrm{LDA}+U$ band-structure calculation have revealed that the first peak crossing $E_F$ consists of the (Fe+Mo) $t_{2g\downarrow }$ states and the second peak well below $E_F$ is dominated by the Fe $e_{g\uparrow }$ states. This clearly shows that only the down-spin states contribute to the $E_F$ intensity, thus the half-metallic density of states (DOS) is realized. We point out that the observed half-metallic DOS can be attributed to the strong Hund’s rule energy stabilization due to the high-spin ${3d}^5$ configuration at the Fe site.