Cr${\mathrm{O}}_2$—A New Half-Metallic Ferromagnet?

Spin-resolved photoemission from polycrystalline Cr${\mathrm{O}}_2$ films shows a spin polarization ($P$) of nearly +100% for binding energies near 2 eV below the Fermi level ($E_{\mathrm{F}}$). Despite the metallic resistivity behavior, extremely low intensity is observed in the photoemission spectra near $E_{\mathrm{F}}$. Our findings are in contrast to recent band-structure calculations, predicting Cr${\mathrm{O}}_2$ to be a half-metallic ferromagnet with $P=+100\%$ at $E_{\mathrm{F}}$.