Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi , New Delhi 110016, India.
Institute of Physics , Sachivalaya Marg, Bhubaneswar 751005, India.
ACS Appl Mater Interfaces. 2017 Sep 13;9(36):31005-31017. doi: 10.1021/acsami.7b06991. Epub 2017 Aug 29.
For achieving ultrafast switching speed and minimizing dissipation losses, the spin-based data storage device requires a control on effective damping (α) of nanomagnetic bits. Incorporation of interfacial antidamping spin orbit torque (SOT) in spintronic devices therefore has high prospects for enhancing their performance efficiency. Clear evidence of such an interfacial antidamping is found in Al capped Py(15 nm)/β-W(t)/Si (Py = NiFe and t = thickness of β-W), which is in contrast to the increase of α (i.e., damping) usually associated with spin pumping as seen in Py(15 nm)/β-W(t)/Si system. Because of spin pumping, the interfacial spin mixing conductance (g) at Py/β-W interface and spin diffusion length (λ) of β-W are found to be 1.63(±0.02) × 10 m (1.44(±0.02) × 10 m) and 1.42(±0.19) nm (1.00(±0.10) nm) for Py(15 nm)/β-W(t)/Si (β-W(t)/Py(15 nm)/Si) bilayer systems. Other different nonmagnetic capping layers (CL), namely, β-W(2 nm), Cu(2 nm), and β-Ta(2,3,4 nm) were also grown over the same Py(15 nm)/β-W(t). However, antidamping is seen only in β-Ta(2,3 nm)/Py(15 nm)/β-W(t)/Si. This decrease in α is attributed to the interfacial Rashba like SOT generated by nonequilibrium spin accumulation subsequent to the spin pumping. Contrary to this, when interlayer positions of Py(15 nm) and β-W(t) is interchanged irrespective of the fixed top nonmagnetic layer, an increase of α is observed, which is ascribed to spin pumping from Py to β-W layer.
为了实现超快的开关速度和最小化耗散损耗，基于自旋的数据存储设备需要控制纳米磁性位的有效阻尼（α）。因此，在自旋电子器件中引入界面反阻尼自旋轨道扭矩（SOT）有望提高它们的性能效率。在 Al 覆盖的 Py（15nm）/β-W（t）/Si 中（Py = NiFe，t 为 β-W 的厚度）发现了这种界面反阻尼的明显证据，这与通常与自旋泵浦相关的 α 的增加（即阻尼）形成对比，在 Py（15nm）/β-W（t）/Si 系统中可以看到。由于自旋泵浦，在 Py/β-W 界面处的界面自旋混合电导（g）和 β-W 的自旋扩散长度（λ）分别为 1.63(±0.02)×10 m（1.44(±0.02)×10 m）和 1.42(±0.19)nm（1.00(±0.10)nm），对于 Py（15nm）/β-W（t）/Si（β-W（t）/Py（15nm）/Si）双层系统。其他不同的非磁性覆盖层（CL），即β-W（2nm）、Cu（2nm）和β-Ta（2、3、4nm）也在相同的 Py（15nm）/β-W（t）上生长。然而，只有在β-Ta（2、3nm）/Py（15nm）/β-W（t）/Si 中才会出现反阻尼。α 的减小归因于自旋泵浦后非平衡自旋积累产生的界面 Rashba 型 SOT。与此相反，当 Py（15nm）和β-W（t）的层间位置互换，而不管固定的顶部非磁性层如何，α 的增加是观察到的，这归因于自旋从 Py 到β-W 层的泵浦。
