摘要
We have studied magnetism in anatase Ti <sub>1-x</sub> Co <sub>x</sub> O <sub>2-δ</sub> (x = 0.05) thin films with various electron carrier densities, by soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L <sub>2,3</sub> absorption edges. For electrically conducting samples, the magnetic moment estimated by XMCD was < 0.3 μ <sub>B</sub> /Co using the surface-sensitive total electron yield mode, while it was 0.3-2.4 μ <sub>B</sub> /Co using the bulk-sensitive total fluorescence yield mode. The latter value is in the same range as the saturation magnetization 0.6-2.1 μ <sub>B</sub> /Co deduced by SQUID measurement. The magnetization and the XMCD intensity increased with carrier density, consistent with the carrier-induced origin of the ferromagnetism. © 2012 American Institute of Physics.