2D transition metal dichalcogenides (TMDs) are excellent candidate materials to study the effect of spin-orbit torques (SOTs). Here, the effect of a WSe₂ underlayer on the magnetic properties and SOT efficiencies are systematically investigated in Pt /Co bilayers with perpendicular magnetic anisotropy. SOT efficiency ξ shows an increasing trend as the inserted WSe₂ monolayer number increases from 0 to 5, which is attributed to the elevated spin absorption at the WSe₂/Pt interface where WSe₂ acts as a spin sink. As the Co layer thickness t_Co increases from 0.6 to 1.0 nm, ξ exhibits a maximum at t_Co = 0.8 nm, which is mainly due to the nonmonotonic change of spin transmission at the Pt/Co interface. Moreover, the ξ value of WSe₂ (5ML) /Pt/Co increases significantly when the measurement temperature decreases, which can be interpreted by the increased spin absorption capability of WSe₂ due to the elevated spin mixing conductance at reduced temperatures. The findings provide deep insight into the origin of robust charge-spin conversion in the TMD/Pt/Co system, which will promote the implementation of advanced SOT devices based on the 2D materials.

中文翻译：

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通过在层下插入 WSe2 极大地提高了 Pt/Co 双层中的自旋轨道扭矩效率

二维过渡金属二硫化物 (TMD) 是研究自旋轨道扭矩 (SOT) 影响的优秀候选材料。在这里，在具有垂直磁各向异性的 Pt/Co 双层中系统地研究了 WSe ₂底层对磁性和 SOT 效率的影响。随着插入的 WSe ₂单层数从 0 增加到 5，SOT 效率 ξ 呈增加趋势，这归因于 WSe ₂ /Pt 界面处的自旋吸收增加，其中 WSe ₂充当自旋槽。随着 Co 层厚度t _Co从 0.6 增加到 1.0 nm，ξ 在t _Co处表现出最大值 = 0.8 nm，这主要是由于 Pt/Co 界面处自旋传输的非单调变化。此外，当测量温度降低时，WSe ₂ (5ML) /Pt/Co的 ξ 值显着增加，这可以解释为 WSe _{2 的}自旋吸收能力增加，因为在降低的温度下自旋混合电导升高。这些发现为深入了解 TMD/Pt/Co 系统中强大的电荷自旋转换的起源提供了深刻的见解，这将促进基于二维材料的先进 SOT 器件的实施。