  A time-resolved ferromagnetic resonance technique was used to investigate the
magnetization dynamics of a 10 nm thin Permalloy film. The experiment consisted
of a sequence of magnetic field pulses at a repetition rate equal to the
magnetic systems resonance frequency. We compared data obtained by this
technique with conventional pulsed inductive microwave magnetometry. The
results for damping and frequency response obtained by these two different
methods coincide in the limit of a small angle excitation. However, when
applying large amplitude field pulses, the magnetization had a non-linear
response. We speculate that one possible cause of the nonlinearity is related
to self-amplification of incoherence, known as the Suhl instabilities.
