Wood's anomaly is a phenomenon discovered in 1902 1, manifesting as a decrease of the reflected waves amplitude due to the excitation of a surface mode that is still investigated in photonics 2. Another curious effect observed in the reflection of obliquely incident waves is the Goos-Hanchen effect (GHE) 3,4, which causes a spatial shift of the reflected waves. One of the configurations suitable for observing both phenomena for spin waves (SWs) is the Gires-Tournois interferometer (GTI) proposed in Ref. 5,6, made of a magnetic stripe placed above the edge of a magnetic layer. We use micromagnetic simulations to study the reflection of an oblique incident SW beam at such a GTI. We identified the resonance conditions required to efficiently excite SW modes in the GTI by the incident SW beam, which give rise to magnonic Wood's anomaly in our system. The amplitude of these modes is confined in the stripe and emits SWs back to the layer; therefore, these modes can be classified as 'leaky-modes'. The consequence of the leaky-mode is the creation of multiple spatially shifted SW beams in the layer parallel to one another. Furthermore, the excitation of the leaky-modes is accompanied by a significant GHE for the primary reflected beam with values spanning between -175 nm and 225 nm with respect to the non-resonant case. In Fig. 1a and 1b we show the distributions of SW intensity for the case with the resonant excitation of a leaky-mode and without the excitation, respectively. In Fig. 1b multiple reflected SW beams are evident. Our findings contribute to understanding and utilizing the interaction of propagating SWs in thin films with the localized leaky-modes. Additionally, an incident beam's excitation of modes in GTI provides a platform for investigations of SWs inelastic scattering on interferometer's modes.
We acknowledge the funding from the Polish National Science Centre project No. UMO-2019/33/B/ST5/02013.