A tenet of special relativity is that no particle can exceed the speed of light. In certain magnetic materials, the maximum magnon group velocity serves as an analogous relativistic limit for the speed of magnetic solitons. Here, we drive domain walls to this limit in a low-dissipation magnetic insulator using pure spin currents from the spin Hall effect. We achieve record current-driven velocities in excess of 4300 meters per second—within ~10% of the relativistic limit—and we observe key signatures of relativistic motion associated with Lorentz contraction, which leads to velocity saturation. The experimental results are well explained through analytical and atomistic modeling. These observations provide critical insight into the fundamental limits of the dynamics of magnetic solitons and establish a readily accessible experimental framework to study relativistic solitonic physics.

狭义相对论的宗旨是没有粒子可以超过光速。在某些磁性材料中，最大磁子群速度充当磁孤子速度的类似相对论极限。在这里，我们利用自旋霍尔效应产生的纯自旋电流，在低耗散磁绝缘体中将畴壁驱动到此极限。我们达到了创纪录的电流驱动速度，每秒超过4300米-在相对论极限的10％以内-并且我们观察到与洛伦兹收缩相关的相对论运动的关键特征，从而导致速度饱和。通过分析和原子建模可以很好地说明实验结果。