Coupling of spin waves with acoustic waves - Nonreciprocal propagation of the surface acoustic waves ScAlN/Si. SAW structures on ScAlN (as piezoelectric material) having magnetostrictive material, Ni and/or CoFeB, of different thicknesses (in the range 10-45 nm), in the composition of the IDT and/or between the IDTs will be manufactured. Resonance frequencies above 4 GHz will be targeted. Fingers and finger/interdigit spacing in the 80-170 nm range will be obtained using advanced nanolithography tools. The SAW/SW coupling will be analysed using S parameters measurements in vicinity of resonance vs. H, at different angles between B and the SAW propagation direction. We will analyse also the angle where we have maximum effect. The SAW/SW coupling will have also as effect the nonreciprocal behaviour (S21 differs from S12). We will try to separate the two components of the non-reciprocity by measuring structures having the magnetic material strip between the IDTs with and without the thin heavy metal (few nm of Pt or W) on the top layer. SAW/SW coupling will be performed at room and cryogenic temperatures (10…30K).

Also, magnetic behaviour of the SAW resonators developed on ScAlN/Si will be analysed. Here we will analyse the variation of the resonance frequency vs. H for the single port SAW structures. Different magnetostrictive metals will be deposited in the composition of the interdigitated transducers (IDTs) as well as different geometric strips in the vicinity of the active IDTs area. The behaviour of the resonance frequency will be analysed in H at room temperature and also at very low temperatures (< 20 K), where we expect that the effect of the H is much more significant. The simulation of the SAW structures will couple the FEM results from Comsol with the analytical method COM. The simulations will also take into account the changes of the Young modulus, E, with the H variation, known as ΔE-effect, which appears in the SAW structures due to the change of the magnetoelastic response upon magnetization.