Evidence for an Exchange Coupling at the Interface between Two Ferromagnetic Films

In a first part, we estimate the effect of dynamic pinning [C. F. Kooi, E. P. Wigen, M. R. Shanabarger, and J. V. Kerrigan, J. Appl. Phys. 35, 791 (1964)] due to two ferromagnetic layers upon the spin-waves resonances in a sandwiched film having a higher magnetization, assuming the interface interaction energy to be of an exchange type. Experiments performed on epitaxial films of Permalloy, symmetrically coupled with two nickel layers of various thicknesses, exhibit results in excellent agreement with theory and provide a reproducible value of the interface energy which is one-tenth of that of the bulk exchange energy.