Spectroscopy of the spin waves of a synthetic antiferromagnet grown on a piezoelectric substrate

Efficient coupling between phonons and magnons requires precise knowledge of their dispersion relations on material platforms that contain magnetic multilayers with versatile high-frequency properties grown on piezoelectric substrates with large electromechanical coupling coefficients. One of these systems is the CoFeB/Ru/CoFeB synthetic antiferromagnet grown on a lithium niobate substrate. We investigate its microwave magnetic properties using a combination of ferromagnetic resonance and propagating spin wave spectroscopy, from which we extract the dispersion relation of the acoustic branch of spin waves. The frequency and the linewidth of this spin wave resonance, its field dependence, and its dispersion relation indicate that the magnetic properties are as good as when grown on standard non-piezoelectric substrates, as well as being in line with theory. The knowledge of the exact dispersion relation of the spin waves in this new material platform opens opportunities to extend microwave acousto-magnonics beyond the use of single layer magnets.