Temperature dependence of transport properties in ZnS-based magnetic tunnel junctions

We have recently evidenced a junction magnetoresistance (JMR) signal of about 5% in magnetic tunnel junctions (MTJs) with ZnS as tunnel barrier layer. The MTJ were grown by magnetron sputtering on Si (1 I 1) substrate at room temperature and have the following structure: Fe 6 nm Cu 30 nm CoFe 1.8 nm Ru 0.8 nm CoFe 3 nm ZnS 2 nm CoFe 1 nm Fe 4 nm Cu 10 nm . Ru 3 nm . The hard magnetic bottom electrode consists of an artificial antiferromagnetic structure in which the rigidity is Ru 3 nm . The hard magnetic bottom electrode consists of an artificial antiferromagnetic structure in which the rigidity is ensured by the antiferromagnetic exchange coupling between two FeCo layers through an Ru spacer layer. The magneto-transport for these MTJ has been studied at various temperatures to gain understanding of the transport mechanism in such junctions. A strong and linear increase of the JMR is observed as the temperature is decreased to reach 10% at a low temperature, while the conductance decreases with decreasing temperature. To understand the mechanism at the origin of these behaviors, the contribution of magnon is taken into account. It is concluded that the observed behaviors are not only related to the magnon contribution but that resonant low-level states inside the barrier can assist the tuneling transport.