Ferromagnetism of cobalt-doped anatase TiO$_2$ studied by bulk- and surface-sensitive soft x-ray magnetic circular dichroism
arXiv:1206.0339 · doi:10.1063/1.4729123
Abstract
We have studied magnetism in anatase Ti$_{1-x}$Co$_x$O$_{2-δ}$ ({\it x} = 0.05) thin films with various electron carrier densities, by soft x-ray magnetic circular dichroism (XMCD) measurements at the Co $L_{2,3}$ absorption edges. For electrically conducting samples, the magnetic moment estimated by XMCD was $<$ 0.3 $μ_B$/Co using the surface-sensitive total electron yield (TEY) mode, while it was 0.3-2.4 $μ_B$/Co using the bulk-sensitive total fluorescence yield (TFY) mode. The latter value is in the same range as the saturation magnetization 0.6-2.1 $μ_B$/Co deduced by SQUID measurement. The magnetization and the XMCD intensity increased with carrier density, consistent with the carrier-induced origin of the ferromagnetism.
Accepted in Applied Physics Letters 2012