Thermal Spin Torque in Double-Barrier Tunnel Junctions with Magnetic

The thermal spin torque induced by the spin-dependent Seebeck effect in double-barrier tunnel junctions is derived considering free-electron and tight-binding calculations. We show that in systems comprising ferromagnetic electrodes and nonmagnetic barriers, the in-plane component of the thermal spin torque is the dominant term, whereas in junctions comprising nonmagnetic electrodes and ferromagnetic barriers, both components, the in-plane and the out-of-plane, are comparable in magnitude. Moreover, larger torque amplitudes up to 3 orders of magnitude are obtained in the second system as a result of the spinfiltering effect; consequently, double-barrier tunnel junctions in the presence of magnetic insulators offer an enhanced thermal spin-torque mechanism for reliable applications. We propose taking advantage of quantum resonant tunneling through resonance states below the Fermi level in these structures that can pave a route toward achieving larger spin-torque efficiencies, even when considering smaller values of the exchange splitting. Furthermore, we identify the parameters needed to tune efficiently these resonant states.

Automated summary

This study investigates the thermal spin torque induced by the spin-dependent Seebeck effect in double-barrier tunnel junctions, revealing different dominant terms in thermal spin torque under different combinations of electrodes and barriers. Quantum resonant tunneling through resonance states below the Fermi level is proposed as a method to achieve higher spin-torque efficiencies.