Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

We compare structural and transport properties of Co₂FeAl (CFA)/MgAl₂O₄ (MAO)/CoFe magnetic tunnel junctions (MTJs) with and without a 1 nm thick CoFe insertion layer. While the two MTJs show a large difference in resistance area (RA) product, there is no significant difference in their stacked structures such as the thickness of an MAO barrier. Temperature (T) dependence of tunneling conductance (G _P and G _AP for parallel and antiparallel configurations, respectively) was investigated for the two MTJs, as well as their tunnel magnetoresistance that exceeds 200%. The most striking feature of the temperature dependence is that non-monotonic change appeared by inserting the CoFe layer, i.e. negative dG _P/dT emerged only in the CFA/1 nm CoFe/MAO/CoFe MTJ. The observed results of G _P and G _AP were analyzed in a model proposed by Hu et al (2016 Phys. Rev. B 94, 094428), in which elastic (spin-conserved) and inelastic (spin-flip scattering) terms were considered. We found that the non-monotonic change observed in T dependence of G _P is associated with dominance of the elastic tunneling term. This study demonstrated that the model analysis of T dependence of G _P can give insight into the microscopic transport mechanism. (paper)