Mode hopping via nonlinear magnon-magnon coupling in a synthetic antiferromagnet

Identifying nonlinear interactions among magnons is crucial for advancing the field of magnonics and developing next-generation spintronic devices. In this work, we report the experimental observation of nonlinear magnon mode hopping and hysteretic behavior in a synthetic antiferromagnet (SAF). Under strong radio-frequency excitation, the magnon system exhibits abrupt transitions between acoustic and optic modes, accompanied by GHz-scale frequency jumps-orders of magnitude larger than previously reported in magnon-based hybrid systems. We further show that this mode hopping is hysteretic, reflecting multistable nonlinear dynamics, and support these findings through theory and micromagnetic simulations. These results establish a new regime of nonlinear magnon dynamics, going beyond previously reported strong-coupling effects, and highlight the potential of SAFs as platforms for magnon-based frequency converters and switches for information processing.