Excitation of Spin Waves in Ferromagnets: Eddy Current and Boundary Condition Effects

The boundary condition for the transverse magnetization is derived when there is a surface anisotropy field Hₛ. Writing the transverse magnetization as αsinkz+βcoskz, we have αβ=-1/2ka+(HₛHₑak), where Hₑ is the exchange field and a the lattice constant. A similar result is found when there is an antiferromagnetic surface layer. For Hₛ≠0 spin-wave modes can be excited by a uniform rf field in a ferromagnet. The power absorbed in each mode in an insulator is calculated as a function of the surface anisotropy field. The excitation of the exchange modes is calculated for a metal with eddy-current damping. The eddy currents are found to have a large effect only on long wavelength spin waves. The line shape in a thick metal plate is calculated for H₀ normal to the plate.