Spin-wave resonance frequency in a ferromagnetic thin film

The spin-wave resonance (SWR) frequency in a ferromagnetic thin film with single-ion surface and bulk anisotropies has been studied by using the linear spin-wave approximation and Green's function techniques. The effects of surface and bulk anisotropies, film thickness, spin quantum number, and external magnetic field on the SWR frequency have been investigated. It is found that the SWR frequencies all increase, as the external magnetic field, the bulk anisotropy, and the spin quantum number increase, respectively. The surface anisotropy affects strongly the SWR frequencies of the middle and low modes (except for the lowest one). With large bulk anisotropy, the surface anisotropy affects mainly the resonance frequency of the lowest spin-wave mode. As the film thickness decreases, the SWR frequency of the same mode increases. The present results direct the method to enhance and adjust the SWR frequency of ferromagnetic thin films. -- Highlights: ► The SWR in a ferromagnetic thin film with single-ion surface and bulk anisotropies has been studied. ► The methods are the linear spin-wave approximation and Green's function technique. ► The effects of surface and bulk anisotropies, film thickness, etc. on the SWR frequency have been investigated. ► Theoretically, this work provides a quantum method to study the SWR frequency of ferromagnetic thin films. ► The present results direct the method to enhance and adjust the SWR frequency of ferromagnetic thin films