Time-resolved x-ray magnetic circular dichroism was used to investigate ferromagnetically coupled CoFe/Ru/NiFe bilayers. The magnetization
dynamics was driven by a continuous wave excitation. The precessional
motion of the individual layers was detected separately by tuning the
x-ray photon energy to the L-3 absorption edge of either Ni or Co.
Using two different waveguide stack geometries in-phase and antiphase
excitation could be selected showing its effect in the measured
precessional signal of the individual layers. In exchange-coupled
bilayer two precessional modes were observed for each layer. The
relative phase angles of the magnetic response between the two layers
were found to be 8 and 133, for the two modes revealed their
quasiacoustic and quasioptic character. (c) 2009 American Institute of
Physics. [DOI: 10.1063/1.3068650]