Intrinsic spin polarized electronic structure of CrO₂ epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO₂. We used CrO₂ epitaxial films on TiO₂(100), which shows a peak at 1eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO₂. In spin-resolved spectra at 40K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (E_F) with an energy gap of 0.5eV below E_F were observed in the spin down (minority spin) state. At 300K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO₂ film, constituting spectroscopic evidence for the half-metallicity of CrO₂ at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d.