Enhancing Magnon–Magnon Coupling Strength to 0.6 GHz in Dion–Jacobson Cu(II)-Hybrid Perovskites by Tuning the Topology of Ligands

Copper(II) hybrid organic–inorganic perovskites (HOIPs) offer a unique platform to explore magnetic interactions responsible for ferro- or antiferromagnetic order; yet, their potential for coherent magnon dynamics, a cornerstone of spintronic technologies, remains underdeveloped. Unlike conventional ferromagnets, the structural parameters influencing magnon generation, propagation, and control in HOIPs are poorly understood. Here, we engineer interlayer and intralayer exchange interactions in A-type Dion–Jacobson (DJ) phase Cu(II)-based HOIPs to achieve robust magnon–magnon coupling. By incorporating short, planar organic ligands, we realize a coupling strength of 0.6 GHz, a hallmark of strong interactions vital for dynamic spin-wave manipulation. Landau–Lifshitz–Gilbert simulations and density functional theory (DFT) reveal that interlayer antiferromagnetic exchange and intralayer easy-plane anisotropy jointly dictate the coupling strength in Cu(II)-halide HOIPs. This work demonstrates how the organic ligand topology can be strategically tailored to modulate magnetic exchange pathways, enabling precise control over spin-wave phenomena.