Evidence for positive spin polarization in Co with SrTiO3 barriers -: art. no. 10c908

Recent negative tunneling magnetoresistance results with epitaxial SrTiO3 and TiO2 tunnel barriers were attributed to tunneling that favor d-like states from Co, resulting in negatively polarized electron tunneling. In order to confirm this, we carried out direct measurements of spin polarization of Co with SrTiO3 barriers using a superconductor as a spin detector. The polarization was observed to be positive (+31 %), in contrast to published results. Furthermore, studies conducted on magnetic tunnel junctionswith SrTiO3 and TiO2 tunnel barriers are consistent with the direct measurements. The implications of our results, for the case of amorphous barriers, in comparison to crystalline barriers is discussed. (c) 2005 American Institute of Physics.