Large angle magnetization precession induced by a short pulsed magnetic field in a 15 nm thick Ni81Fe19 film is observed using a time-resolved magneto-optical Kerr effect technique with sensitivity to all three components of the magnetization vector. A reduction of the magnitude of the magnetization vector |M| during large angle precession is inferred and indicates incoherent dynamics due to excitation of traveling spin waves with wavelengths smaller than the sampling area, i.e., the laser spot size for the magneto-optical measurements. The reduction in |M| depends on the magnetic bias field Hbias, which can be qualitatively understood by comparison to the theoretical threshold to observe four-magnon scattering in a small time interval t. We estimate that two-magnon scattering cannot explain the experimental results.
Citation: Physical Review B
Pub Type: Journals
magnetization dynamics, nanomagnetics