Bulk and Surface Magnetization of Co atoms in Rutile Ti_[1-x]Co_xO_[2-delta] Thin Films Revealed by X-Ray Magnetic Circular Dichroism

摘要

We have studied magnetism in Ti_[1-x]Co_xO_[2-\delta] thin films with variousx and \delta by soft x-ray magnetic circular dichroism (XMCD) measurements atthe Co L_[2,3] absorption edges. The estimated ferromagnetic moment by XMCD was0.15-0.24 \mu\beta/Co in the surface, while in the bulk it was 0.82-2.25\mu\beta/Co, which is in the same range as the saturation magnetization of1.0-1.5 \mu\beta/Co. Theseresults suggest that the intrinsic origin of theerromagnetism. The smaller moment of Co atom at surface is an indication of amagnetically dead layer of a few nm thick at the surface of the thin films.