  The resonant interaction of electrically excited travelling surface acoustic
waves and magnetization has been hitherto probed through the acoustic
component. In this work it is investigated using time-resolved magneto-optical
detection of magnetization dynamics. To that end, we develop an experimental
scheme where laser pulses are used both to generate the acoustic wave frequency
and to probe magnetization dynamics thus ensuring perfect phase locking. The
light polarization dependence of the signal enables to disentangle elasto-optic
and magneto-optic contributions and to obtain the in-plane and out-of-plane
dynamic magnetization components. Magnetization precession is proved to be
driven solely by the acoustic wave. Its amplitude is shown to resonate at the
same field at which we detect piezo-electrically the resonant attenuation of
the acoustic wave, clearly evidencing the magneto-acoustic resonance with high
sensitivity.
