Analyses of intrinsic magnetoelectric properties in spin-valve-type tunnel junctions with high magnetoresistance and low resistance

A series of experimental data was obtained systematically for a spin-valve-type tunnel junction of ${\mathrm{Ta}\mathrm{}\left(5\mathrm{}\mathrm{}\mathrm{n}\mathrm{m}\right)/\mathrm{N}\mathrm{i}}_{79}{\mathrm{Fe}}_{21}$ (3 nm)/Cu ${\left(20\mathrm{}\mathrm{}\mathrm{n}\mathrm{m}\right)/\mathrm{N}\mathrm{i}}_{79}{\mathrm{Fe}}_{21}$ ${\left(3\mathrm{}\mathrm{}\mathrm{n}\mathrm{m}\right)/\mathrm{I}\mathrm{r}}_{22}{\mathrm{Mn}}_{78}{\mathrm{}\left(10\mathrm{}\mathrm{}\mathrm{n}\mathrm{m}\right)/\mathrm{C}\mathrm{o}}_{75}{\mathrm{Fe}}_{25}$ (4 nm)/Al ${\left(0.8\mathrm{}\mathrm{}\mathrm{n}\mathrm{m}\right)-\mathrm{o}\mathrm{x}\mathrm{i}\mathrm{d}\mathrm{e}/\mathrm{C}\mathrm{o}}_{75}{\mathrm{Fe}}_{25}$ ${\left(4\mathrm{}\mathrm{}\mathrm{n}\mathrm{m}\right)/\mathrm{N}\mathrm{i}}_{79}{\mathrm{Fe}}_{21}$ (20 nm)/Ta (5 nm). Analyses of (i) temperature dependence of tunnel magnetoresistance (TMR) ratio and resistance from 4.2 K to room temperature, (ii) applied dc bias-voltage dependence of TMR ratio and resistance at 6.0 K and room temperature, and (iii) tunnel current I and dynamic conductance $\mathrm{}(dI/dV)\mathrm{}$ as functions of dc bias voltage at 6.0 K were carried out. High-TMR ratio of 64.7% at 4.2 K and 44.2% at room temperature were observed for this junction after annealing at 300 °C for an hour. An anisotropic wavelength cutoff energy of spin-wave spectrum in magnetic tunnel junctions, which is essential for self-consistent calculations, was suggested based on a series of inelastic electron tunnel spectra obtained. The main intrinsic magnetoelectric properties in such spin-valve-type tunnel junction with high magnetoresistance and low resistance can be evaluated based on the magnon-assisted inelastic excitation model and theory.