Mumax3-cQED: An extension of Mumax3 to simulate magnon-photon interactions in cavity QED
Description
We present Mumax3-cQED, a code for modeling magnon–polaritons in realistic experimental settings. It is an extension of the widely used micromagnetic simulation package Mumax3, building on its GPU-accelerated implementation. To our knowledge, Mumax3-cQED is the first numerical framework that enables the self-consistent simulation of hybrid cavity–ferromagnet dynamics at the micromagnetic level within a single model, without treating the cavity and magnetic subsystems separately. We validate the implementation by benchmarking against numerical and analytical results from the Dicke model in both the paramagnetic and superradiant phases. Mumax3-cQED accurately captures non-equilibrium dynamics and relaxation toward equilibrium. The code also enables the straightforward calculation of hybrid magnon–photon polaritons, as demonstrated by quantitative agreement with experimental observations. Finally, we highlight the potential of Mumax3-cQED for designing magnon–cavity experiments, particularly in scenarios involving strongly inhomogeneous cavity fields or complex magnetization configurations. The software is open-source and provides a versatile tool for studying microscopic saturated ferromagnets as well as spin textures, including domain walls, vortices, and skyrmions.