Novel aspects and strong correlation in the electronic structure of Sr$_2$FeMoO$_6$

We investigate the electronic structure of Sr$_2$FeMoO$_6$ combining photoemission spectroscopy with a wide range of photon energies and electronic structure calculations based on first-principle as well as model Hamiltonian approaches to reveal several interesting aspects. We find evidence for unusually strong Coulomb correlation effects both in the Fe 3$d$ and O 2$p$ states, with an enhanced manifestation in the majority spin channel. Additionally, O 2$p$ states exhibit a spin-splitting of nonmagnetic origin, which nevertheless is likely to have subtle influence on the stability of novel ferromagnetism of this compound.