Radiation damping in ferromagnetic resonance induced by a conducting spin sink

Spin pumping describes the flow of a spin current from a ferromagnet into an adjacent conductor due to spin precession or thermal gradients in the ferromagnet. To measure its magnitude, often the damping of the ferromagnet in ferromagnetic resonance is investigated, which increases when spin pumping takes place. However, in the experiments shown here, it is shown that electromagnetic interactions between the ferromagnet and the conducting nonmagnet with the exciting magnetic radio-frequency field can also cause additional damping. This so-called radiation damping can mimic spin pumping where none exists or at least considerably falsify the results obtained from the standard evaluation of the experiment.