Vortex rings are remarkably stable structures that occur in a large variety of systems, such as in turbulent gases (where they are at the origin of weather phenomena)¹, fluids (with implications for biology)², electromagnetic discharges³ and plasmas⁴. Although vortex rings have also been predicted to exist in ferromagnets⁵, they have not yet been observed. Using X-ray magnetic nanotomography⁶, we imaged three-dimensional structures forming closed vortex loops in a bulk micromagnet. The cross-section of these loops consists of a vortex–antivortex pair and, on the basis of magnetic vorticity (a quantity analogous to hydrodynamic vorticity), we identify these configurations as magnetic vortex rings. Although such structures have been predicted to exist as transient states in exchange ferromagnets⁵, the vortex rings we observe exist as static configurations, and we attribute their stability to the dipolar interaction. In addition, we observe stable vortex loops intersected by point singularities⁷ at which the magnetization within the vortex and antivortex cores reverses. We gain insight into the stability of these states through field and thermal equilibration protocols. The observation of stable magnetic vortex rings opens up possibilities for further studies of complex three-dimensional solitons in bulk magnets, enabling the development of applications based on three-dimensional magnetic structures.

涡环是非常稳定的结构，它存在于多种系统中，例如湍流气体（它们是天气现象的起源）¹，流体（对生物学有影响）²，电磁放电³和等离子体⁴。尽管也已预言在铁磁体^5中存在涡流环，但尚未观察到它们。使用X射线磁纳米断层扫描⁶，我们对三维结构进行了成像，这些三维结构在体微磁体中形成了闭合的涡流环。这些环的横截面由一个涡旋-反涡旋对组成，并且根据磁涡旋（类似于流体动力涡旋的量），我们将这些配置标识为磁涡旋环。尽管已经预测这样的结构在交换铁磁体^5中作为瞬态存在，但我们观察到的涡旋环以静态构型存在，并且我们将其稳定性归因于偶极相互作用。此外，我们观察到由点奇异点相交的稳定涡旋环⁷涡旋和反涡旋磁芯内的磁化强度反转。我们通过现场和热平衡协议深入了解了这些状态的稳定性。稳定的磁涡流环的观察为进一步研究块状磁体中的复杂三维孤子开辟了可能性，从而使基于三维磁性结构的应用得以发展。