Zhou Hangyu, Zhang Youguang, Zhao Weisheng
School of Electronic and Information Engineering, Beihang University, Beijing 100191, China.
School of Integrated Circuit Science and Engineering, MIIT Key Laboratory of Spintronics, Beihang University, Beijing 100191, China.
ACS Appl Mater Interfaces. 2021 Jan 13;13(1):1214-1221. doi: 10.1021/acsami.0c17829. Epub 2020 Dec 30.
Two-dimensional (2D) van der Waals (vdW) heterostructures have opened new avenues for spintronic applications with novel properties. Here, by density functional theory calculations, we investigated the spin-dependent transport in vdW magnetic tunnel junctions (MTJs) composed of 1-CrTe ferromagnetic electrodes. Meanwhile, graphene and -BN are employed as tunnel barriers. It has been found that the tunneling magnetoresistance (TMR) effects of two types of vdW MTJs present analogous trends: thicknesses of barriers have a great influence on the TMR ratios, which reach up to the maximum when barriers increase to five monolayers. However, despite the similarity, the graphene-barrier junction is more promising for optimization. Through observing the energy-resolved transmission spectra of vdW MTJs, we noticed that TMR ratios of graphene-barrier junctions are tunable and could be enhanced through tuning the position of Fermi energy. Therefore, we successfully realized the TMR optimization by substitutional doping. When substituting one carbon atom with one boron atom in the graphene barrier, TMR ratios are drastically improved, and a TMR ratio as high as 6962% could be obtained in the doped seven-monolayer-barrier junction. Our results pave the way for vdW MTJ applications in spintronics.
二维（2D）范德华（vdW）异质结构为具有新颖特性的自旋电子学应用开辟了新途径。在此，通过密度泛函理论计算，我们研究了由1-CrTe铁磁电极组成的vdW磁隧道结（MTJ）中的自旋相关输运。同时，采用石墨烯和-BN作为隧道势垒。已发现两种类型的vdW MTJ的隧道磁电阻（TMR）效应呈现类似趋势：势垒厚度对TMR比率有很大影响，当势垒增加到五个单原子层时，TMR比率达到最大值。然而，尽管存在相似性，但石墨烯势垒结在优化方面更具前景。通过观察vdW MTJ的能量分辨透射光谱，我们注意到石墨烯势垒结的TMR比率是可调的，并且可以通过调整费米能级的位置来提高。因此，我们通过替代掺杂成功实现了TMR优化。当在石墨烯势垒中用一个硼原子替代一个碳原子时，TMR比率大幅提高，在掺杂的七个单原子层势垒结中可获得高达6962%的TMR比率。我们的结果为vdW MTJ在自旋电子学中的应用铺平了道路。
