Ding Shilei, Wang Hanchen, Legrand William, Noël Paul, Gambardella Pietro
Department of Materials, ETH Zürich, 8093 Zürich, Switzerland.
Nano Lett. 2024 Aug 21;24(33):10251-10257. doi: 10.1021/acs.nanolett.4c02613. Epub 2024 Aug 12.
Charge-spin interconversion processes underpin the generation of spin-orbit torques in magnetic/nonmagnetic bilayers. However, efficient sources of spin currents such as 5 metals are also efficient spin sinks, resulting in a large increase of magnetic damping. Here we show that a partially oxidized 3 metal can generate a strong orbital torque without a significant increase in damping. Measurements of the torque efficiency ξ and Gilbert damping α in CoFe/CuO and CoFe/Pt indicate that ξ is comparable in the two systems. The increase in damping relative to a single CoFe layer is Δα < 0.002 in CoFe/CuOx and Δα ≈ 0.005-0.02 in CoFe/Pt, depending on CoFe thickness. We ascribe the nonreciprocal relationship between Δα and ξ in CoFe/CuO to the small orbital-spin current ratio generated by magnetic resonance in CoFe and the lack of an efficient spin sink in CuO. Our findings provide new perspectives on the efficient excitation of magnetization dynamics via the orbital torque.
电荷 - 自旋相互转换过程是磁/非磁双层中自旋 - 轨道转矩产生的基础。然而，诸如5种金属这样的高效自旋电流源也是高效的自旋汇，导致磁阻尼大幅增加。在此我们表明，部分氧化的3种金属能够产生强大的轨道转矩，而不会使阻尼显著增加。对CoFe/CuO和CoFe/Pt中转矩效率ξ和吉尔伯特阻尼α的测量表明，这两个系统中的ξ相当。相对于单个CoFe层，CoFe/CuOx中的阻尼增加量Δα < 0.002，而CoFe/Pt中的Δα约为0.005 - 0.02，这取决于CoFe的厚度。我们将CoFe/CuO中Δα与ξ之间的非互易关系归因于CoFe中磁共振产生的小轨道 - 自旋电流比以及CuO中缺乏有效的自旋汇。我们的发现为通过轨道转矩高效激发磁化动力学提供了新的视角。
