Monotonically decreasing ferromagnetic resonance linewidth of Cu/Ni_0.81Fe_0.19 bilayer heterostructures with the increasing sputtering rate of the Cu layer

Permalloy with low ferromagnetic resonance linewidth has great application potential in spintronic/microwave devices. In this work, we demonstrated that the nonmagnetic (Cu) layer's sputtering rate has a considerable impact on Ni_0.81Fe_0.19's linewidth in Cu (4 nm)/Ni_0.81Fe_0.19 (3 nm) bilayer heterostructures. A monotonically decreasing out-of-plane linewidth was displayed as the sputtering rates increased from 0.27 to 1.75 Å/s due to interdiffusion. Meanwhile, a large reduction of the in-plane linewidth from 18.54 to 7.83 mT was also obtained from suppressing the interfacial inhomogeneity and two-magnon scattering effects. The present work contributes to a clearer understanding of Cu/Ni_0.81Fe_0.19 nanoscale films' interfacial inhomogeneity and opens a new road on tailoring magnetodynamic properties.