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 Ta(5nm)/Ni₇₉Fe₂₁ (3 nm)/Cu (20nm)/Ni₇₉Fe₂₁ (3nm)/Ir₂₂Mn₇₈(10nm)/Co₇₅Fe₂₅ (4 nm)/Al (0.8nm)-oxide/Co₇₅Fe₂₅ (4nm)/Ni₇₉Fe₂₁ (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 $(dI/dV)$ 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.