Investigation of Mode‐Induced Spin Wave Transmission Blockage by In Situ Nanoscale Grooves

Abstract In the pursuit of advancing spin‐wave optics, the propagation of magnetostatic surface spin‐waves is investigated in a uniform permalloy waveguide with in‐situ nanopatterned grooves created through Atomic Force Microscopy nanolithography and Focused Ion Beam etching. The study unveils that the introduction of narrow constrictions and grooves leads to a non‐monotonic reduction of the transmitted spin‐wave signal intensity as the spin‐wave pathway is shrinked. The remarkable feature that a stronger signal extinction is obtained for a narrow groove compared to a spin‐waveguide interrupted by a full gap, where only inefficient transport through dipolar coupling is allowed, is highlighted. Combining experimental and numerical analyses, the intricate interplay between spin‐wave diffraction and reflection at the waveguide edges is unraveled, being at the origin of a transverse‐mode variation responsible for the signal extinction when detected using coplanar antennas. The findings offer insights into the controllable manipulation of detected spin‐wave intensity, thereby opening promising avenues for the improvement of spin‐wave switches and interferometers, and for the nanopatterning of graded index magnonics.