Tuning the permeability spectra with a half-free ferromagnetic underlayer in (NiFe/IrMn)n exchange-biased multilayers

► Adding ferromagnetic underlayer can broaden the ferromagnetic resonance linewidth. ► 2.4 GHz ferromagnetic resonance linewidth has been obtained. ► We fit the permeability spectra based on the Landau-Lifshitz-Gilbert equation. ► Both damping parameters and effective dynamic anisotropy fields are obtained. ► A flexible ferromagnetic resonance linewidth-tuning approach is proposed.