Generation of gigahertz-frequency surface acoustic waves in Y₃Fe₅O₁₂/ZnO heterostructures

We study surface acoustic waves (SAWs) in yttrium iron garnet (YIG)/zinc oxide (ZnO) heterostructures, comparing the results of a computationally lightweight analytical model with time-resolved microfocused Brillouin light scattering (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mtext fontfamily="times">μ</a:mtext></a:math>-BLS) data. Interdigital transducers (IDTs), with operational frequencies in the gigahertz regime, were fabricated on 50-nm and 100-nm thin films of YIG prior to sputter deposition of 830-nm and 890-nm films of piezoelectric ZnO. We find good agreement between our analytical model and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><e:mtext fontfamily="times">μ</e:mtext></e:math>-BLS data of the IDT frequency response and SAW group velocity, with clear differentiation between the Rayleigh-like and Sezawa-like modes. Finally, nonreciprocal coupling between SAWs and spin waves (SWs) is shown. This work paves the way for a detailed study of the interaction between SAWs and SWs in low SW damping YIG, with the possibility of a method for future energy-efficient SW excitation.