Light scattering from thermal magnons in iron and nickel

Light scattering measurements from thermal acoustic magnons have been performed for the first time in the metals iron and nickel. A three-pass-plus-two-pass tandem Fabry-Perot interferometer was used to analyze the backscattered light from the polycrystalline or single crystal samples. The magnetic field was parallel to the sample surface and perpendicular to the plane of incidence. Two modes can be observed: bulk magnons and surface magnons. The dependence of the frequency on the applied field for iron can be described by a magnetostatic dispersion relation for an insulating ferromagnet. In nickel the measured frequencies are considerably higher than predicted. Some of the problems arising from the metallic character of the samples are discussed.