Lv Yang, Kally James, Zhang Delin, Lee Joon Sue, Jamali Mahdi, Samarth Nitin, Wang Jian-Ping
Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
Department of Physics, The Pennsylvania State University, University Park, PA, 16802, USA.
Nat Commun. 2018 Jan 9;9(1):111. doi: 10.1038/s41467-017-02491-3.
The large spin-orbit coupling in topological insulators results in helical spin-textured Dirac surface states that are attractive for topological spintronics. These states generate an efficient spin-orbit torque on proximal magnetic moments. However, memory or logic spin devices based upon such switching require a non-optimal three-terminal geometry, with two terminals for the writing current and one for reading the state of the device. An alternative two-terminal device geometry is now possible by exploiting the recent discovery of the unidirectional spin Hall magnetoresistance in heavy metal/ferromagnet bilayers and unidirectional magnetoresistance in magnetic topological insulators. Here, we report the observation of such unidirectional magnetoresistance in a technologically relevant device geometry that combines a topological insulator with a conventional ferromagnetic metal. Our devices show a figure of merit (magnetoresistance per current density per total resistance) that is more than twice as large as the highest reported values in all-metal Ta/Co bilayers.
拓扑绝缘体中的大自旋轨道耦合导致了具有螺旋自旋纹理的狄拉克表面态，这对拓扑自旋电子学具有吸引力。这些态在近端磁矩上产生有效的自旋轨道转矩。然而，基于这种开关的存储器或逻辑自旋器件需要一种非最优的三端几何结构，其中两个端子用于写入电流，一个用于读取器件状态。通过利用最近在重金属/铁磁体双层中发现的单向自旋霍尔磁电阻以及磁性拓扑绝缘体中的单向磁电阻，现在可以实现另一种两端器件几何结构。在此，我们报告了在一种将拓扑绝缘体与传统铁磁金属相结合的具有技术相关性的器件几何结构中观察到这种单向磁电阻。我们的器件显示出一个品质因数（每电流密度每总电阻的磁电阻），该品质因数比在全金属Ta/Co双层中报道的最高值大两倍多。
