X-ray photoemission spectroscopy measurements were performed on thin-film samples of rutile ${\mathrm{Ti}}_{1-x}{\mathrm{Co}}_x{\mathrm{O}}_{2-\delta }$ to reveal the electronic structure. The Co $2p$ core-level spectra indicate that the Co ions take the high-spin ${\mathrm{Co}}^{2+}$ configuration, consistent with substitution on the Ti site. The high-spin state and the shift due to the exchange splitting of the conduction band suggest strong hybridization between carriers in the Ti $3d$ $t_{2g}$ band and the $t_{2g}$ states of the high-spin ${\mathrm{Co}}^{+2}$. These observations support the argument that room temperature ferromagnetism in ${\mathrm{Ti}}_{1-x}{\mathrm{Co}}_x{\mathrm{O}}_{2-\delta }$ is intrinsic.

• Received 23 February 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.027202