Excitation and Boundary Effects in Spin-Wave Resonance

Using the general spin-wave dispersion relation and the general exchange boundary condition, the spin-wave absorption spectrum in a Permalloy film is calculated. Whereas the spacings between the various spin-wave resonance peaks are largely dependent upon the value of the exchange constant A, the result of the calculation shows that the relative intensities of the absorption peaks are dependent upon both A and the surface anisotropy energy density Ks. Thus, the value of Ks can be obtained by comparing the relative experimental intensities of the various peaks with the calculated results using various values of assumed Ks. Though the resonance intensities are also dependent upon the ratio of the rf magnetic fields at the two surfaces of the film, an experimental configuration may be devised such that the ratio of the two fields is near unity. In this way, |Ks| for Permalloy films was estimated to be from 1 to 3 erg/cm2.