In an FMR experiment, a ferromagnetic sample is placed in a uniform magnetic field and exposed to microwave radiation. The magnetization within the sample precesses around the direction of the applied magnetic field. When the frequency of the microwave radiation matches the precession frequency of the magnetization, resonance occurs, leading to the absorption of microwave energy. This resonance condition is described by the Kittel equation: ω = γ(Heff + 2πMs) where ω is the angular frequency of the microwave radiation, γ is the gyromagnetic ratio, Heff is the effective magnetic field, and Ms is the saturation magnetization.
