Magnetic torques generated through spin–orbit coupling^{1,2,3,4,5,6,7,8} promise energy-efficient spintronic devices. For applications, it is important that these torques switch films with perpendicular magnetizations without an external magnetic field^{9,10,11,12,13,14}. One suggested approach¹⁵ to enable such switching uses magnetic trilayers in which the torque on the top magnetic layer can be manipulated by changing the magnetization of the bottom layer. Spin currents generated in the bottom magnetic layer or its interfaces transit the spacer layer and exert a torque on the top magnetization. Here we demonstrate field-free switching in such structures and show that its dependence on the bottom-layer magnetization is not consistent with the anticipated bulk effects¹⁵. We describe a mechanism for spin-current generation^16,17 at the interface between the bottom layer and the spacer layer, which gives torques that are consistent with the measured magnetization dependence. This other-layer-generated spin–orbit torque is relevant to energy-efficient control of spintronic devices.

通过自旋轨道耦合^{1,2,3,4,5,6,7,8}产生的磁转矩有望实现节能的自旋电子设备。对于应用而言，重要的是这些扭矩可在没有外部磁场的情况下切换具有垂直磁化强度的薄膜^{9,10,11,12,13,14}。一种建议的方法¹⁵为了实现这种切换，请使用磁性三层，其中可以通过更改底层的磁化强度来控制顶层磁性层上的扭矩。在底部磁性层或其界面中产生的自旋电流穿过隔离层，并在顶部磁化强度上施加扭矩。在这里，我们展示了这种结构中的无场切换，并表明其对底层磁化强度的依赖性与预期的体积效应¹⁵不一致。我们描述了自旋电流产生的机制^16,17在底层和隔离层之间的界面处，其扭矩与测得的磁化强度相关。这种由其他层产生的自旋轨道扭矩与自旋电子设备的节能控制有关。