  We present a time-resolved measurement of magnetization dynamics during
ferromagnetic resonance (FMR) in a single layer of Ni81Fe19. Small-angle (<1
deg.) precession of elemental Ni, Fe moments could be measured directly and
quantitatively using time-resolved x-ray magnetic circular dichroism (XMCD) in
transmission. The high temporal and rotational sensitivity of of this technique
has allowed characterization of the phase and amplitude of driven FMR motion at
2.3 GHz, verifying basic expectations for a driven resonance.
