Layer-dependent magnon-magnon coupling in a synthetic antiferromagnet

作者：Yaqi Rong, Chengxin Jiang, Huishan Wang, Lu Sun, Fengyu Liu, Juanjuan Lu, Tao Wu, Yu Zhang, Yunshan Zhao, Fusheng Ma, Zhiqiang Mu, Haomin Wang, Yumeng Yang · 发表于：Physical Review Applied · 年份：2024 · DOI：10.1103/physrevapplied.21.054050 · 被引用次数：11 · 研究领域：Physics of Superconductivity and Magnetism、Magnetic properties of thin films、Mechanical and Optical Resonators

The synthetic antiferromagnet (SAF) offers a versatile platform to couple with various quasiparticles that is an indispensable element for the realization of hybrid quantum computing systems. In this work, we found that the magnon-magnon coupling strength in layered SAFs, consisting of repeated layers of $[{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}/\mathrm{Ru}{]}_{n}$, is highly dependent on the finite layer number n. In particular, the self-hybridizations of individual acoustic or optical modes in the even-layers lead to the opening of local anticrossing gaps within the same type of mode in the resonance spectra. With the structural asymmetry of the odd-layers, a global gap between different modes can be generated whose size is found to decrease with increasing layer number. By combining the static linear chain model with the dynamically coupled Landau-Lifshitz equations, we further formulated a theoretical approach to qualitatively describe such highly layer-dependent behaviors of magnon-magnon coupling in SAFs. It is clear that the layer number is a significant factor that influences both the number of excited modes and the associated mode hybridizations. Our findings shed light on the magnon-magnon coupling in layered antiferromagnets that may invigorate the development of magnonics.