Unidirectional spin waves measured using propagating-spin-wave spectroscopy

In some magnetic materials, spin-wave dispersion relations vary monotonically across the Brillouin zone, allowing wave packets with zero momentum to flow unidirectionally, which points to high-frequency spintronic applications. To get there, though, it is crucial to develop methods that can link a spin wave's properties to experimentally accessible metrics. To this end, the authors use propagating-spin-wave spectroscopy to precisely measure the dispersion of unidirectional spin waves. Their method identifies the wave vector at a particular frequency, which was a limiting factor in previous studies. This metrological approach is sure to impact the study of thin-film magnetism.