Anomalous Hall effect in anatase Co:TiO2 ferromagnetic semiconductor

We have investigated the effects of modification of the SrTiO3 /Co interface as well as the SrTiO3 barrier on the tunnel magnetoresistance TMR of La0.67Sr0.33MnO3 /SrTiO3 /Co junctions. Modification was realized by the introduction of one atomic layer of either TiO2 or SrO at the SrTiO3 /Co interface. Barriers with different oxygen content were also studied. In these structures we have observed positive as well as negative TMR, with a trend towards positive TMR for junctions with interfacial SrO and/or more oxygen-deficient barriers. This work offers more insight into the SrTiO3 /Co tunnel spin polarization and its sign