Green's function modeling of the magnetoresistance of magnetic tunnel junctions exhibiting quasiparticle bands

Through the non-equilibrium Green's function description of electron transport in magnetic tunnel junctions (MTJs), we investigate the tunnel magnetoresistance (TMR) of a model MTJ described by the s-f Hamiltonian. The method allows us to study the bias and temperature dependence of the TMR as well as the influence of different material characteristics such as the band width, band occupation, exchange splitting of the bands etc. on the TMR. We find from our study that the magnetic correlations present in the ferromagnetic electrodes suppress the TMR heavily and it strongly alters the behavior of the TMR with respect to the applied bias too. Our study reveals that the TMR is significantly influenced by the band occupation of the metallic electrodes. The origin of the substantial changes in the TMR with respect to the band occupation, applied bias and temperature is analyzed through the calculation of the spin-dependent tunnel current in the parallel and antiparallel configuration of the magnetization of the ferromagnetic electrodes