A Self-consistent Calculation and an Anisotropic Wavelength Cutoff Energy of Spin-wave Spectrum in Magnetic Tunnel Junctions

Temperature dependence of tunnel magnetoresistance (TMR) ratio,resistance, and coercivity from 4.2 K to room temperature (RT), applied dc bias voltage dependence of the TMR ratio and resistances at 4.2 K and RT, tunnel current I and dynamic conductance dI/dV as functions of the dc bias voltage at 4.2 K, and inelastic electron tunneling (lET) spectroscopy, d2I/dV2 versus V,at 4.2 K for a tunnel junction of Ta(5 nm)/Ni79Fe21(25 nm)/Ir22Mn78(12 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide/Co75Fe25(4 nm)/Ni79Fe21(25 nm)/Ta(5 nm) were systematically investigated.High TMR ratio of 59.2% at 4.2 K and 41.3% at RT were observed for this junction after annealing at 275℃ for an hour. The temperature dependence of TMR ratio and resistances from 4.2 to 300 K at 1.0 mV bias and the dc bias voltage dependence of TMR ratio at 4.2 K from 0 to 80 mV can be evaluated by a comparison of self-consistent calculations with the experimental data based on the magnon-assisted inelastic excitation model and theory. An anisotropic wavelength cutoff energy of spin-wave spectrum in magnetic tunnel junctions (MTJs)was suggested, which is necessary for self-consistent calculations, based on a series of lET spectra observed in the MTJs.