Regensburg 2022 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 28: Magnonics 2

MA 28.4: Vortrag

Donnerstag, 8. September 2022, 10:15–10:30, H43

Investigation of Spin Wave Caustics Phenomena — •Franz Vilsmeier¹, Alexis Wartelle², Takuya Taniguchi¹, and Christian Back¹ — ¹Technische Universität München — ²Grenoble Institute of Technology

We present a systematic survey of caustic spin wave beams and their properties in an anisotropic magnetic environment.

Based on the theory from Kalinikos and Slavin for spin waves in soft films [Journal of Physics C: Solid State Physics, 1986, 19, 7013-7033], an anisotropic dispersion relation allows caustic points to exist. Here, several wavevectors with the same group velocity direction can be excited over a broad angular range within the sample plane. These caustic points result in nondiffractive spin wave beams and are characterised by their propagation direction, wavefront angle and wavelength.

Experimentally, we excite the caustic points in 200 nm thick Yttrium Iron Garnet by sending an rf current through a bow-shaped antenna. Time Resolved Kerr Microscopy is used to investigate the propagation behaviour both, spatially, as well as time resolved. We are able to access one caustic pocket and detect caustic-like beams over a range of different rf frequencies and external magnetic field values. Furthermore, the caustic-like beams are used to directly observe anisotropic reflection phenomena and steering of the beams with rotation of the externally applied field. The findings are compared to micromagnetic simulations with the help of Mumax3.