  Soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L2,3
edges of Co doped rutile TiO2 at room temperature have revealed clear multiplet
features characteristic of ferromagnetic Co2+ ions coordinated by O2- ions,
being in sharp contrast to the featureless XMCD spectrum of Co metal or
metallic clusters. The absorption and XMCD spectra agree well with a full
atomic-multiplet calculation for the Co2+ high-spin state in the D2h-symmetry
crystal field at the Ti site in rutile TiO2. The results indicate that the
ferromagnetism arises from the Co2+ ions substituting the Ti4+ ions.
