Ferromagnetic resonance (FMR) measured over a large range of frequencies from 1–70 GHz offers a unique possibility to study the dynamic response of ultrathin ferromagnetic films in the range from nanoseconds to picoseconds. The linewidth of the FMR signal is commonly believed to follow a linear $\omega$ dependence, the so-called Gilbert damping. Here we give experimental unambiguous evidence that other processes of spin dynamics such as two-magnon scattering are equally important at interfaces of ferromagnetic to nonmagnetic nanostructures. The relevance to spin transport and spin injection as well as the agreement with recent theoretical proposals are discussed.

• Received 20 June 2003

DOI:https://doi.org/10.1103/PhysRevB.68.060102