  We experimentally study magnetization dynamics in magnetic tunnel junctions
driven by femtosecond-laser-induced surface acoustic waves. The acoustic pulses
induce a magnetization precession in the free layer of the magnetic tunnel
junction through magnetoelastic coupling. The frequency and amplitude of the
precession shows a pronounced dependence on the applied magnetic field and the
laser excitation position. Comparing the acoustic-wave-induced precession
frequencies with precession induced by charge currents and with micromagnetic
simulations we identify spatially non-uniform magnetization modes localized
close the edge regions as being responsible for the optically induced
magnetization dynamics. The experimental scheme even allows us to coherently
control the magnetization precession using two acoustic pulses. This might
prove important for future applications requiring ultrafast spin manipulation.
Additionally, our results directly pinpoint the importance of acoustic pulses
since they could be relevant when investigating optically-induced temperature
effects in magnetic structures.
