Enhanced thermal spin transfer in MgO-based double-barrier tunnel junctions

Based on atomic first principles, we predict enhanced thermal spin transfer (TST) effects and small switching temperature gradient in Fe $|$ MgO $|$ Fe $|$ MgO $|$ Fe double-barrier magnetic tunnel junctions (MTJs). At room temperature, temperature gradient $\Delta T$ ∼10 $K$ with $\nabla T$ ∼10 K nm⁻¹ across barriers would be sufficient to switch the magnetic configurations circularly in a junction with 3 MgO atomic layers (L), which is about one order smaller than that in Fe $|$ MgO(3L)$|$ Fe MTJs. This temperature gradient is under the current experimental capability. The resonant quantum-well states in companion with resonant interfacial states are responsible for the enhancement. Moreover, a thermal induced 'off' state is found in a double-barrier MTJ. (paper)