A GHz operating ScAlN based SAW resonator used for Surface Acoustic Waves/Spin Waves Coupling

A thin ScAlN layer was deposited on high resistivity (111) oriented silicon and two port surface acoustic wave (SAW) devices were manufactured, using advanced nanolithographic techniques, on this material. The Surface Acoustic Wave and Spin Wave (SAW/SW) coupling was performed via a thin ferromagnetic layer (Ni) placed between the interdigitated transducers (IDTs) of the SAW device. Since the phase velocity in this material is lower than in the Si substrate, both Rayleigh (4.67 GHz) and Sezawa (8.05 GHz) propagation modes could be observed. The amplitude of the S₂₁ parameter around the two resonances was measured for values of the magnetic field µ₀H from -280 to +280 mT, at different angles (θ) between the SAW propagation direction and the magnetic field direction. A maximum decrease of 2.54 dB occurred in S₂₁ for the Rayleigh mode at µ₀H = -90 mT, and of 7.24 dB for the Sezawa mode at µ₀H =-203 mT, both at θ = 45°. These values were extracted from time gated processing of the frequency domain raw data.