We report an experimental observation of magnon-magnon coupling in interlayer exchange coupled synthetic antiferromagnets of $\mathrm{FeCoB}/\mathrm{Ru}/\mathrm{FeCoB}$ layers. An anticrossing gap of spin-wave resonance between acoustic and optic modes appears when the external magnetic field points to the direction tilted from the spin-wave propagation. The magnitude of the gap (i.e., coupling strength) can be controlled by changing the direction of the in-plane magnetic field and also enhanced by increasing the wave number of excited spin waves. We find that the coupling strength under the specified conditions is larger than the dissipation rates of both the resonance modes, indicating that a strong coupling regime is satisfied. A theoretical analysis based on the Landau-Lifshitz equation shows quantitative agreement with the experiments and indicates that the anticrossing gap appears when the exchange symmetry of two magnetizations is broken by the spin-wave excitation.

中文翻译：

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合成反铁磁体中动态偶极相互作用介导的可调磁振子-磁振子耦合。

我们报告了在层间交换耦合合成反铁磁体中的磁振子-磁振子耦合的实验观察。 $\mathrm{铁钴}/茹/\mathrm{铁钴}$层。当外部磁场指向自旋波传播倾斜的方向时，会在声学和光学模式之间出现自旋波共振的反交叉间隙。可以通过改变面内磁场的方向来控制间隙的大小（即，耦合强度），并且还可以通过增加激发的自旋波的波数来增加间隙的大小。我们发现，在指定条件下的耦合强度大于两个共振模式的耗散率，这表明满足了强耦合条件。基于Landau-Lifshitz方程的理论分析表明与实验具有定量一致性，并且表明当自旋波激发破坏两个磁化的交换对称性时出现反交叉间隙。