Analytic expression for the giant fieldlike spin torque in spin-filter magnetic tunnel junctions

We propose analytic expressions for fieldlike, T, and spin-transfer, T, spin torque components in the spin-filter-based magnetic tunnel junction (SFMTJ), by using the single-band tight-binding model with the nonequilibrium Keldysh formalism. In consideration of multireflection processes between noncollinear magnetization of the spin-filter (SF) barrier and the ferromagnetic (FM) electrode, the central spin-selective SF barrier plays an active role in the striking discovery TT, which can be further identified by the unusual barrier thickness dependence of giant T. Our general expressions reveal the sinusoidal angular dependence of both spin torque components, even in the presence of the SF barrier.