  We present micromagnetic simulations of the dynamic GHz-range resonance modes
of skyrmions excited by either out-of-plane ac magnetic fields or spin torques
in prototypical synthetic ferri- and antiferromagnetic trilayer structures. The
observed features in the calculated power spectra exhibit a systematic
dependence on the coupling strength between the individual magnetic layers and
are related to pure in-phase and anti-phase breathing modes as well as to
hybridizations of breathing and spin-wave modes that are characteristic for the
considered circular-shaped geometry. The experimental detection of these
resonant oscillation modes may provide a means for skyrmion sensing
applications and for the general characterization of skyrmion states in
multilayer stacks with antiferromagnetic interlayer exchange coupling.
