Relaxation and Nonlinear Effects in Ferromagnetic Thin Films

Abstract

In the first part, the authors give curves of ΔH versus the thickness d of the films magnetized normal and parallel to the film plane. One can see that ΔH⊥ (normal case) does not vary with d whereas ΔH∥ (parallel case) increases with d. Using the classical dispersion curves of degenerate spin waves, the authors conclude that internal imperfections are not responsible of the variations of ΔH∥ but it seems that the main source of scattering may be due to the edges of the films. In the second part, the preliminary results of the behavior of thin films with high microwave power are given. The bulk sample theory of Suhl predicts that no subsidiary absorption is present. In the measurement of our films (f=9.3 GHz and 4πM = 104 Oe), the experimental curves exhibit a subsidiary absorption and a saturation of the uniform resonance mode, similar results being obtained with other samples. Finally, the authors give the variations of χ″/χ0″ with P/Pc and conclude that these curves can be used to obtain some information concerning the internal or surface imperfections of the films.