In magnetic materials, a disturbance in the local spin ordering can propagate as a wave. Such spin waves carry information and as they do not suffer from the heating effects associated with moving charges they are touted as potential data carriers for next-generation computing devices. But for this to happen, the propagation of spin waves needs to be predictable and controllable. Johannes Stigloher and co-workers have now shown that a rule analogous to Snell's Law in optics can explain how spin waves travel between two media.
Snell's Law describes how light waves refract at the interface between different media. By exciting spin waves in a thick permalloy film and watching how they propagate into a film with a lower thickness, which has a different dispersion relation, Stigloher et al. probed the refractive behaviour of spin waves. For low incidence angles, they showed that the refraction and reflection of spin waves in the dipolar regime could be described by a law similar to Snell's. And although deviations are found at large incidence angles, this provides a clear route for both predicting and controlling the propagation of spin waves.
Rights and permissions
About this article
Cite this article
Fleet, L. Law and order. Nature Phys 12, 723 (2016). https://doi.org/10.1038/nphys3858