Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA.
Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, USA.
Nat Commun. 2014;5:3042. doi: 10.1038/ncomms4042.
Spin-orbit interaction-driven phenomena such as the spin Hall and Rashba effect in ferromagnetic/heavy metal bilayers enables efficient manipulation of the magnetization via electric current. However, the underlying mechanism for the spin-orbit interaction-driven phenomena remains unsettled. Here we develop a sensitive spin-orbit torque magnetometer based on the magneto-optic Kerr effect that measures the spin-orbit torque vectors for cobalt iron boron/platinum bilayers over a wide thickness range. We observe that the Slonczewski-like torque inversely scales with the ferromagnet thickness, and the field-like torque has a threshold effect that appears only when the ferromagnetic layer is thinner than 1 nm. Through a thickness-dependence study with an additional copper insertion layer at the interface, we conclude that the dominant mechanism for the spin-orbit interaction-driven phenomena in this system is the spin Hall effect. However, there is also a distinct interface contribution, which may be because of the Rashba effect.
自旋轨道相互作用驱动的现象，如铁磁体/重金属双层中的自旋霍尔和拉什巴效应，使得通过电流有效地控制磁化成为可能。然而，自旋轨道相互作用驱动现象的基本机制仍未解决。在这里，我们开发了一种基于磁光克尔效应的灵敏自旋轨道扭矩磁强计，该磁强计可测量钴铁硼/铂双层在很宽的厚度范围内的自旋轨道扭矩矢量。我们观察到，类似于斯隆采维奇的扭矩与铁磁体的厚度成反比，而场型扭矩则存在一个阈值效应，只有当铁磁层厚度小于 1nm 时才会出现。通过在界面处添加附加的铜插入层的厚度依赖性研究，我们得出结论，该体系中自旋轨道相互作用驱动现象的主要机制是自旋霍尔效应。然而，也存在明显的界面贡献，这可能是由于拉什巴效应。
