Anomalous Hall effect suppression in anatase Co:TiO2 by the insertion of an interfacial TiO2 buffer layer

We present the effect of introducing a TiO2 buffer layer at the SrTiO3/Co:TiO2 interface on the magnetic and structural properties of anatase Co:TiO2 (1.4 at. % Co). Inserting the buffer layer leads to suppression of the room-temperature anomalous Hall effect, accompanied by a reduced density of Co clusters, and a different depth distribution of such clusters. Co clusters in Co:TiO2 with a buffer layer are mostly formed at the surface, such that they are situated outside the current path and cannot contribute to the transverse anomalous Hall resistivity. These results indicate extrinsic origins of magnetism in anatase Co:TiO2.