Modulation of magnon lifetime through magnon–magnon coupling

Abstract

The dynamic control of magnon lifetime via magnon–magnon coupling (MMC) is crucial for spintronic applications, yet the underlying mechanisms governing the evolution of dynamical parameters during the coupling process in synthetic antiferromagnets (SAFs) remain elusive. Here, time-resolved polar magneto-optical Kerr effect measurements are employed to investigate the magnon dynamics in a symmetric SAF thin film. By applying a tilted external magnetic field, parity symmetry breaking is induced, leading to the observation of anticrossing gaps in the frequency–field (f–H) dispersion and the emergence of MMC. By tracking the magnon relaxation, abrupt lifetime crossovers are observed near the frequency anticrossing points, and the MMC strength is found to dominate the width of such crossover region. These experimental findings are in good agreement with numerical simulations. A unified physical picture is proposed to account for the lifetime crossovers together with the other two dynamical responses under MMC, all of which constitute key signatures of magnon hybridization. Our study provides direct experimental evidence of MMC-induced mode transformation and demonstrates a viable strategy for manipulating magnon lifetimes in SAF systems.