Ferrimagnetic alloys are model systems for understanding the ultrafast magnetization switching in materials with antiferromagnetically coupled sublattices. Here we investigate the dynamics of the rare-earth and transition-metal sublattices in ferrimagnetic GdFeCo and TbCo dots excited by spin–orbit torques with combined temporal, spatial and elemental resolution. We observe distinct switching regimes in which the magnetizations of the two sublattices either remain synchronized throughout the reversal process or switch following different trajectories in time and space. In the latter case, we observe a transient ferromagnetic state that lasts up to 2 ns. The asynchronous switching of the two magnetizations is ascribed to the master–agent dynamics induced by the spin–orbit torques on the transition-metal and rare-earth sublattices and their weak antiferromagnetic coupling, which depends sensitively on the alloy microstructure. Larger antiferromagnetic exchange leads to faster switching and shorter recovery of the magnetization after a current pulse. Our findings provide insight into the dynamics of ferrimagnets and the design of spintronic devices with fast and uniform switching.

亚铁磁合金是用于理解具有反铁磁耦合子晶格的材料中的超快磁化转换的模型系统。在这里，我们研究了由自旋轨道扭矩激发的亚铁磁 GdFeCo 和 TbCo 点中稀土和过渡金属亚晶格的动力学，并结合了时间、空间和元素分辨率。我们观察到不同的切换机制，其中两个亚晶格的磁化强度要么在整个反转过程中保持同步，要么按照不同的时间和空间轨迹进行切换。在后一种情况下，我们观察到持续长达 2 ns 的瞬态铁磁状态。两种磁化强度的异步切换归因于过渡金属和稀土亚晶格上的自旋轨道转矩及其弱反铁磁耦合引起的主剂动力学，这敏感地取决于合金微观结构。较大的反铁磁交换导致电流脉冲后更快的切换和更短的磁化恢复。我们的研究结果提供了对铁磁体动力学和具有快速均匀开关的自旋电子器件设计的深入了解。