Nonreciprocal transmission of magnetoacoustic waves in compensated synthetic antiferromagnets

We investigate the interaction between surface acoustic waves (SAWs) and spin (SWs) in a Pt/Co($2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$)/Ru($0.85\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$)/Co($2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$)/Pt compensated synthetic antiferromagnet (SAF) composed of two ferromagnetic layers with equal thicknesses separated by thin nonmagnetic Ru spacer layer. Because combined presence interlayer dipolar coupling fields interfacial Dzyaloshinskii--Moriya (iDMI), optical SW mode shows large nondegenerate dispersion relation for counter-propagating SWs. Due to resonant SAW-SW interaction, we observe nonreciprocal SAW transmission prepared piezoelectric/SAF hybrid device. demonstrate that nonreciprocity symmetric SAFs magnetic can show substantially different characteristic behavior comparison asymmetric or single iDMI. For SAF, shift magnetoacoustic resonance excitation efficiency depend on external field sweep direction. one direction angle field, propagating are larger than opposite In addition, magnitude is at minimum if aligned perpendicular propagation The experimental results agreement phenomenological model.