Singh Simranjeet, Katoch Jyoti, Zhu Tiancong, Meng Keng-Yuan, Liu Tianyu, Brangham Jack T, Yang Fengyuan, Flatté Michael E, Kawakami Roland K
Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
Optical Science and Technology Center and Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA.
Phys Rev Lett. 2017 May 5;118(18):187201. doi: 10.1103/PhysRevLett.118.187201. Epub 2017 May 2.
Two-dimensional materials provide a unique platform to explore the full potential of magnetic proximity-driven phenomena, which can be further used for applications in next-generation spintronic devices. Of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene-ferromagnetic-insulator (FMI) heterostructures. Here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to FMI magnetization. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. Additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the nonlocal spin signals in graphene, which is due to spin relaxation by thermally induced transverse fluctuations of the FMI magnetization.
二维材料为探索磁近邻驱动现象的全部潜力提供了一个独特的平台，该现象可进一步用于下一代自旋电子器件的应用。特别令人感兴趣的是，在石墨烯-铁磁绝缘体（FMI）异质结构中，通过附近铁磁材料的磁交换场来理解和控制石墨烯中的自旋电流。在此，我们展示了一项实验研究，该研究表明，通过控制由于FMI磁化产生的交换场方向，可以对石墨烯层中的自旋电流进行强调制。由于界面干净，强磁交换耦合导致在短石墨烯通道中，在低外部施加磁场下实验观察到完全的自旋调制。此外，我们发现石墨烯自旋电流可以被随机波动的交换场完全退相。这表现为石墨烯中非局域自旋信号异常强烈的温度依赖性，这是由于FMI磁化的热诱导横向波动导致的自旋弛豫。
