Shiota Yoichi, Taniguchi Tomohiro, Ishibashi Mio, Moriyama Takahiro, Ono Teruo
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
National Institute of Advanced Industrial Science and Technology (AIST), Spintronic Research Center, Tsukuba, Ibaraki 305-8568, Japan.
Phys Rev Lett. 2020 Jul 3;125(1):017203. doi: 10.1103/PhysRevLett.125.017203.
We report an experimental observation of magnon-magnon coupling in interlayer exchange coupled synthetic antiferromagnets of FeCoB/Ru/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.
我们报道了在FeCoB/Ru/FeCoB层的层间交换耦合合成反铁磁体中磁振子-磁振子耦合的实验观察结果。当外部磁场指向偏离自旋波传播方向倾斜的方向时，声学模式和光学模式之间会出现自旋波共振的反交叉间隙。该间隙的大小（即耦合强度）可以通过改变面内磁场的方向来控制，并且也可以通过增加激发自旋波的波数来增强。我们发现，在特定条件下的耦合强度大于两种共振模式的耗散率，这表明满足强耦合条件。基于朗道-里夫希茨方程的理论分析与实验结果在定量上相符，并表明当自旋波激发破坏了两个磁化强度的交换对称性时会出现反交叉间隙。
