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

Abstract

The recently synthesized two-dimensional van der Waals (vdW) ferromagnet 1T-${\mathrm{MnSe}}_{2}$ has attracted great attention due to its room-temperature ferromagnetism. By using ab initio quantum transport simulations 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 ${\mathrm{MnSe}}_{2}$/n-layer graphene/${\mathrm{MnSe}}_{2}$ (n = 1--4) vdW magnetic tunnel junctions (MTJs). A surprising tunneling magnetoresistance of around ${10}^{6}$% is obtained when $\ensuremath{\theta}={180}^{\ensuremath{\circ}}$ and n = 4 owing to the nearly perfect spin polarization; this is 3 orders of magnitude larger than that of the commonly used $\mathrm{MgO}$-based MTJ (1000% at 5 K). The maximal linear-response spin-transfer torque of the ${\mathrm{MnSe}}_{2}$/graphene/${\mathrm{MnSe}}_{2}$ MTJ (5260 \textmu{}eV/V) is 2 orders of magnitude larger than that of the $\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}$ MTJ. The decay rate of the spin-transfer torkance at zero bias is revealed to be nonmonotonically n dependent. 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-${\mathrm{MnSe}}_{2}$-based vdW MTJs are promising in next-generation room-temperature nonvolatile memories.