  We generate in-plane magnetoelastic waves in nickel films using the
all-optical transient grating technique. When performed on amorphous glass
substrates, two dominant magnetoelastic excitations can be resonantly driven by
the underlying elastic distortions, the Rayleigh Surface Acoustic Wave and the
Surface Skimming Longitudinal Wave. An applied field, oriented in the sample
plane, selectively tunes the coupling between magnetic precession and one of
the elastic waves, thus demonstrating selective excitation of coexisting, large
amplitude magnetoelastic waves. Analytical calculations based on the Green's
function approach corroborate the generation of the non-equilibrium surface
acoustic transients.
