Thickness-dependence of magnetic damping related to two-magnon scattering in ultrathin Ni_0.81Fe_0.19films

Magnetic damping is of critical importance for devices due to its influences on magnetization dynamics. When the ferromagnetic layer goes into the nanometer scale, the magnetic damping related to the two-magnon scattering (TMS) effect becomes the main damping in nonmagnetic/ferromagnetic films. Here, we experimentally demonstrated the thickness-dependence of TMS damping, one part dependent on ferromagnetic thickness ( tFM ), another part independent, in both Cu/NiFe and Pt/NiFe films. The tFM-2 scale of TMS damping can be explained based on the 'Arias-Mills' mode, and its origin is the distribution of surface magnetic anisotropy due to interface defects. The rest of TMS damping is independent on tFM is attributed to the more generic defects creating inhomogeneity, and its origin can be sorted into the 'McMichael-Krivosik' mechanism. The quantitative results reveal that the tFM-2 -dependent and tFM -independent TMS damping are of equal importance in ultrathin NiFe films. Meanwhile, the approximately equal intrinsic damping was displayed for Cu/NiFe and Pt/NiFe thin films. Our results add a clearer understanding of TMS damping in ultrathin ferromagnetic films.