1College of Physics and Information Engineering, Shanxi Normal University, Taiyuan 030031, China 2Key Laboratory of Magnetic Molecules and Magnetic Information Materials of the Ministry of Education, Research Institute of Materials Science, Shanxi Normal University, Taiyuan 030031, China 3International Center for Quantum Design of Functional Materials, University of Science and Technology of China, Hefei 230026, China 4Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
Abstract：The van der Waals heterojunctions, stacking of different two-dimensional materials, have opened unprecedented opportunities to explore new physics and device concepts. Here, combining the density functional theory with non-equilibrium Green's function technique, we systematically investigate the spin-polarized transport properties of van der Waals magnetic tunnel junctions (MTJs), Cu/MnBi$_{2}$Te$_{4}$/MnBi$_{2}$Te$_{4}$/Cu and Cu/MnBi$_{2}$Te$_{4}$/h-BN/$n\cdot$MnBi$_{2}$Te$_{4}$/Cu ($n=1$, 2, 3). It is found that the maximum tunnel magnetoresistance of Cu/MnBi$_{2}$Te$_{4}$/h-BN/3$\cdot$MnBi$_{2}$Te$_{4}$/Cu MTJs can reach 162.6%, exceeding the system with only a single layer MnBi$_{2}$Te$_{4}$. More interestingly, our results indicate that Cu/MnBi$_{2}$Te$_{4}$/h-BN/$n\cdot$MnBi$_{2}$Te$_{4}$/Cu ($n=2$, 3) MTJs can realize the switching function, while Cu/MnBi$_{2}$Te$_{4}$/h-BN/3$\cdot$MnBi$_{2}$Te$_{4}$/Cu MTJs exhibit the negative differential resistance. The Cu/MnBi$_{2}$Te$_{4}$/h-BN/3$\cdot$MnBi$_{2}$Te$_{4}$/Cu in the parallel state shows a spin injection efficiency of more than 83.3%. Our theoretical findings of the transport properties will shed light on the possible experimental studies of MnBi$_{2}$Te$_{4}$-based van der Waals magnetic tunneling junctions.
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