The contributions of intrinsic damping and two magnon scattering on the ferromagnetic resonance linewidth in [Fe65Co35/SiO2]n multilayer films

In order to investigate microwave damping mechanisms of ferromagnetic films with a structure of [ferromagnetic (FM)/non-magnetic insulator (NMI)]n, a serial of [Fe65Co35/SiO2]n multilayer films was prepared by a magnetron sputtering method on the glass substrate. As-prepared films show excellent soft magnetic properties with tiny coercivities along the easy and hard axis respectively, and remarkable in-plane unixial anisotropies were observed too. The microwave properties were characterized by the ferromagnetic resonance (FMR) and a broadband permeameter. The corresponding theoretical fitting was conducted based on the Landau–Lifshitz–Gilbert (LLG) and two magnon scattering (TMS) theory. Fitting results show the TMS linewidth has a value of 36 times bigger than Landau–Lifshitz intrinsic linewidth, which gives a quantitative and explicit physical picture of microwave damping mechanisms in [Fe65Co35/SiO2]n multilayer films and may be important for the understanding of damping in [FM/NMI]n multilayer films.

The angle dependence FMR linewidth of multilayer film [Fe65Co35/SiO2]20 was fitted using a modified two magnon scattering (TMS) theory, while θ = 0°, there is essentially no TMS contribution but the L–L intrinsic damping is nonzero. As θ increases, both contributions rise up very sharply and subsequently diminish rapidly while θ > 4.2°. The linewidth from TMS is 1.65 times as big as the L–L damping linewidth while θ = 4.2°. As the external field is rotated into the film plane at θ = 90°, the L–L linewidth reduces to the same value as θ = 0° but TMS linewidth slightly drops to a value of 36 times bigger than L–L linewidth. It is no doubt that in our multilayer sample, the TMS contribution is the most important origin of the microwave damping, which mainly comes from the imperfection in interfaces and pores in those layers.Figure optionsDownload as PowerPoint slideHighlights
► We believe that our method to research the damping mechanisms of magnetic multilayer films is interesting to general readers of Journal of Alloys and Compound.
► In the paper, the ferromagnetic resonance technology and a microwave permeameter combined with the corresponding theoretical fit were used to investigate the damping origins of multilayer films.
► A quantitative relationship between the intrinsic and extrinsic damping has been obtained and two magnon scattering loss was proved to be the main extrinsic damping mechanism of [Fe65Co35/SiO2]20 multilayer film, which is important for the understanding of damping in multilayer films.