Layer-Dependent Magnetoresistance and Spin-Transfer Torque in MnSe2-Based Magnetic Tunnel Junctions

The recently synthesized two-dimensional van der Waals (vdW) ferromagnet 1T-MnSe2 has attracted great attention due to its room-temperature ferromagnetism. By using ab initio quantum transport sim-ulations with noncollinear spins, we demonstrate a monotonic increasing (decreasing) tendency of the angle-resolved tunneling magnetoresistance (spin-transfer torque) with the increasing graphene layer number n in the MnSe2/n-layer graphene/MnSe2 (n = 1-4) vdW magnetic tunnel junctions (MTJs). A surprising tunneling magnetoresistance of around 106% is obtained when theta = 180 degrees and n = 4 owing to the nearly perfect spin polarization; this is 3 orders of magnitude larger than that of the com-monly used MgO-based MTJ (1000% at 5 K). The maximal linear-response spin-transfer torque of the MnSe2/graphene/MnSe2 MTJ (5260 mu eV/V) is 2 orders of magnitude larger than that of the Fe/MgO/Fe MTJ. The decay rate of the spin-transfer torkance at zero bias is revealed to be nonmonotonically n depen-dent. Meanwhile, the total spin-transfer torque in the device changes from linear dependence to nonlinear dependence as the bias voltage increases. Our calculation suggests that the 1T-MnSe2-based vdW MTJs are promising in next-generation room-temperature nonvolatile memories.