Properties Of Surface Spin Waves In Magnetic Thin Films

In this paper,the quantum statistical Green's function method and Heisenberg model are used to study the spin spectrum,spin wave density of states,surface spin wave and spin wave spatial distribution of symmetric and asymmetric magnetic thin films.The effects of temperature,external magnetic field,surface exchange coupling,surface anisotropy and film thickness on the region of existence and frequency of surface spin wave in two-dimensional Brillouin zone are investigated.For symmetrical and asymmetrical magnetic thin films,as the temperature and the external magnetic field increase,the region of existence of the acoustic and optical surface spin wave is first increased and then decreased.The region of existence of acoustic surface spin wave in a magnetic thin films with easy plane surface anisotropy is larger than that in a magnetic thin films with easy axis surface anisotropy.The region of existence of optical surface spin wave in a magnetic thin films with easy plane surface anisotropy is smaller than that in a magnetic thin films with easy axis surface anisotropy.It is found that there are several special frequency ranges in which interesting spin wave distributions occur in thin films.For symmetrical magnetic thin films,with the increase of surface exchange coupling,the region of existence of acoustic surface spin wave decreases,while that of optical surface spin wave increases.The region of existence of surface spin wave increases with the increase of thin film thickness.The frequency of acoustic and optical surface spin wave decreases with the increase of temperature and increases with the increase of external magnetic field.Acoustic and optical surface spin wave frequencies increase with the increase of surface exchange coupling and surface anisotropy,but surface exchange coupling and surface anisotropy have greater influence on the frequency of acoustic surface spin wave.With the increase of the thickness of magnetic thin films,the frequency of acoustic and optical surfaces spin waves increases.For asymmetric magnetic thin films,the existence region of acoustic surface spin wave decreases with the increase of lower surface exchange coupling,but the existence region of optical surface spin wave is almost unchanged.With the increase of the upper surface exchange coupling,the existence region of optical surface spin wave increases,while theexistence region of acoustic surface spin wave is almost unchanged.The change of the lower surface anisotropy has little effect on the existence region of optical surface spin wave,while the change of the upper surface anisotropy has little effect on the existence region of acoustic surface spin wave.The existence region of surface spin wave decreases with the increase of film thickness.The results of this paper enrich the basic knowledge of surface spin waves in magnetic thin films,which are beneficial to the establishment of microwave devices based on magnetic thin films in the future.