Investigation of the tunnel magnetoresistance in junctions with a strontium stannate barrier

摘要

We experimentally investigate the structural, magnetic, and electrical transport properties of La_(0.67) Sr_(0.33)MnO_3 based magnetic tunnel junctions with a SrSnO_3 barrier. Our results show that despite the high density of defects in the strontium stannate barrier, due to the large lattice mismatch, the observed tunnel magnetoresistance (TMR) is comparable to tunnel junctions with a better lattice matched SrTiO_3 barrier, reaching values of up to 350% at T = 5 K. Further analysis of the current-voltage characteristics of the junction and the bias voltage dependence of the observed tunnel magnetoresistance show a decrease of the TMR with increasing bias voltage. In addition, the observed TMR vanishes for T ＞ 200 K. Our results suggest that by employing a better lattice matched ferromagnetic electrode, and thus reducing the structural defects in the strontium stannate barrier, even larger TMR ratios might be possible in the future.