Spin transfer torque in magnetic tunnel junctions with synthetic ferrimagnetic layers

Based on the spin-polarized free-electron model, spin and charge transports are analyzed in the magnetic tunnel junctions with the synthetic ferrimagnetic layers in the ballistic regime, and the spin-transfer torque is derived. In the realistic junctions, the spin torque exerted on the magnetizations of two ferromagnetic layers in the synthetic ferrimagnetic layer shows a trend to rotate the same direction. It is suggested that, through the antiferromagnetic interlayer coupling in the synthetic ferrimagnetic layer, this trend induces the cooperative reversal of magnetizations in two ferromagnetic layers, and expected that this cooperative rotation reduces the critical current for the magnetization reversal in the synthetic ferrimagnetic layer.