Ferromagnetism induced by clustered Co in Co-doped anatase TiO2 thin films -: art. no. 017401

We investigated ferromagnetism of a newly discovered ferromagnetic semiconductor Co-doped anatase TiO2 thin film, using the magnetic circular dichroism (MCD) at the Co L-2,L-3 absorption edges. The magnetic moment was observed to be similar to0.1mu(B)/Co in the measurements, but the MCD spectral line shape is nearly identical to that of Co metal, showing that the ferromagnetism is induced by a small amount of clustered Co. With thermal treatments at similar to400degreesC, the MCD signal increases, and the moment reaches up to similar to1.55mu(B)/Co, which is similar to90% of the moment in Co metal. In the latter case, the cluster size was observed to be 20-60 nm.