Layer-Dependent Magnetoresistance and Spin-Transfer Torque in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>MnSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>-Based Magnetic Tunnel Junctions
Baochun Wu, Jie Yang, Shiqi Liu, Shibo Fang, Zhou Liu, Zhongchong Lin, Junjie Shi, Wenyun Yang, Zhaochu Luo, Changsheng Wang, Honglin Du, Jinbo Yang, Jing Lü
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.