Anisotropic Magnon–Magnon Coupling in Synthetic Antiferromagnets
Wei He, Z. K. Xie, Rui Sun, Meng Yang, Yang Li, Xiao-Tian Zhao, Wei Liu, Z. D. Zhang, Jian-Wang Cai, Zhao-Hua Cheng, Jie Lu
Abstract
Magnon–magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies. To induce magnon–magnon coupling, the parity symmetry between two magnetization needs to be broken. Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure. We successfully introduce a magnon–magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir( t Ir = 0.6 nm, 1.2 nm)/CoFeB(13 nm). Remarkably, we find that the weakly uniaxial anisotropy field (∼ 20 Oe) makes the magnon–magnon coupling anisotropic. The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for t Ir = 0.6 nm, and between 0.09 GHz and 1.4 GHz for t Ir = 1.2 nm. Our results demonstrate a feasible way to induce magnon–magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field. The magnon–magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.