Temperature dependence of spin-dependent tunneling conductance of magnetic tunnel junctions with half-metallic C o2MnSi electrodes

Abstract

In order to elucidate the origin of the temperature (T) dependence of spin-dependent tunneling conductance (G) of magnetic tunnel junctions (MTJs), we experimentally investigated the T dependence of G for the parallel and antiparallel magnetization alignments, GP and GAP, of high-quality Co2MnSi (CMS)/MgO/CMS MTJs having systematically varied spin polarizations (P) at 4.2 K by varying the Mn composition α in Co2MnαSi electrodes that exhibited giant tunneling magnetoresistance ratios. Results showed that GP normalized by its value at 4.2 K exhibited a notable, nonmonotonic T dependence although its variation with T was significantly smaller than that of GAP normalized by its value at 4.2 K, indicating that an analysis of the experimental GP(T) is critical to revealing the origin of the T dependence of G. By analyzing the experimental GP(T), we clarified that both spin-flip inelastic tunneling via a thermally excited magnon and spin-conserving elastic tunneling in which P decays with increasing T play key roles. The experimental GAP(T), including its stronger T dependence for higher P at 4.2 K, was also consistently explained with this model. Our findings provide a unified picture for understanding the origin of the T dependence of G of MTJs with a wide range of P, including MTJs with high P close to a half-metallic value.