Magnetism is well-known to inherently break time-reversal symmetry; for example, the magnetization precesses in a single (counter-clockwise) direction around its equilibrium axis. By integrating a magnetic thin film onto a piezoelectric substrate, enabling phonons to hybridize with magnons, we show that this intrinsic nonreciprocity can be transferred to surface acoustic waves.
Surface acoustic wave (SAW) filter: Two interdigitated transducers (IDT1 and IDT2) generate elastic surface waves in a piezoelectric crystal, which then interact with a magnetic garnet thin film deposited on the same surface.
Surface acoustic wave (SAW) filters are at the forefront of modern wireless electronics. Their slow propagation speed (~1000 m/s) enables the design of compact filters for the microwave frequency range. Achieving one-way acoustic transport is crucial for using the same device as both a transmitter and a receiver. Here, we propose to realize this functionality by integrating a thin film of the ferrimagnetic insulator yttrium iron garnet (Y3Fe5O12, YIG) into the device, as illustrated in the figure. YIG is particularly attractive due to its low magnetic damping and long magnon relaxation time.
While magnetoelastic interactions between YIG and SAWs have been used to implement acoustic isolators, achieving on-chip SAW-driven magnetic resonance has been challenging due to material-device integration constraints. In this work, we demonstrate nonreciprocal resonant SAW absorption in an on-chip YIG-SAW device fabricated using focused-ion-beam techniques. Multiple absorption peaks are observed, corresponding to perpendicular standing spin wave (PSSW) modes, with higher-order PSSWs exhibiting pronounced nonreciprocity when the SAW propagation direction is reversed. These observations are consistent with theoretical models that account for asymmetric surface conditions and nonreciprocal magnon-SAW coupling.
The strong nonreciprocal SAW attenuation in YIG offers a promising pathway toward highly efficient RF signal processing. Our results establish on-chip YIG-SAW devices as a versatile platform for studying nonreciprocal SAW absorption, magnon-phonon interactions, and advanced YIG-based magnonic technologies.
Teams: Spin Insulatronics
Collaborations: RIKEN et ISSP Tokyo (JP)
Funding: Q-SPIN chaire d’excellence LANEF portée avec le Prof. YoshiChika Otani
Further reading: Nonreciprocal Resonant Surface Acoustic Wave Absorption in \({Y}{₃}{Fe}₅O₁₂\), Y. Ba, J. Puebla, K. Yamamoto, Y. Hwang, L. Liao, S. Maekawa, O. Klein, and Y. Otani, Physical Review B 111, 104401 (2025). Open access: cea-05003586v1
Contact: Olivier Klein
