Tunneling magnetoresistance with positive and negative sign in La0.67 Sr0.33 MnO3 SrTiO3 Co junctions

Abstract

We have investigated the effects of modification of the SrTiO3 Co interface as well as the SrTiO3 barrier on the tunnel magnetoresistance (TMR) of La0.67 Sr0.33 MnO3 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. © 2007 The American Physical Society.