Magnon–magnon coupling in noncollinear synthetic antiferromagnets

We report a theoretical analysis of magnon–magnon coupling in a noncollinear magnetic sandwiched structure with interlayer exchange interaction, which consists of two ferromagnetic layers with perpendicular and in-plane magnetic anisotropy, respectively. Based on the Landau–Lifshitz equation, the spin wave dispersion is derived, and then the frequency gap is observed due to the magnon–magnon coupling effect induced by symmetry breaking. The influence of saturation magnetization, exchange coupling interaction, perpendicular magnetic anisotropy, and wave vector on the coupling strength is studied in detail. We find that the coupling strength is strongly dependent on the saturation magnetization and a small saturation magnetization can lead to strong coupling strength. By selecting the appropriate magnetic materials, the ultra-strong coupling regime can be achieved. The precession information in time domain is solved and the alternating change of the precession components in two ferromagnetic layers implies the exchange of energy and information.