The origin of bias-voltage dependence in CoFe/SrTiO3/La0.7Sr0.3MnO3 magnetic tunnel junctions

The relationship between the oxidized state in a barrier and the bias-voltage dependence on tunnel magnetoresistance (TMR) effect was examined in Co90Fe10/SrTiO3(STO)/La0.7Sr0.3MnO3(LSMO) magnetic tunnel junctions using single crystalline LSMO electrode and STO barrier. A TMR junction, whose STO barrier was fabricated stoichiometrically, exhibited an asymmetric dependence with regard to the bias direction. However, when the STO barrier had an oxygen deficiency, the TMR ratio was reduced symmetrically. The oxygen deficiency of the STO barrier is probably the cause of the oxygen deficiency in the interfacial LSMO and the electron scattering in the barrier, and they may reduce the symmetric bias-voltage dependence. (C) 2002 American Institute of Physics.