  Surface acoustic waves (SAWs) coupled to magnons have attracted much
attention because they allow for the long-range transport of magnetic
information which cannot be achieved by magnon alone. We employed pulsed laser
interferometry to visualize the entire spatiotemporal dynamics of a SAW that
travels on a nickel (Ni) thin film and is coupled to magnons. It was possible
to trace the coupling-induced amplitude reduction and phase shift that occurs
as the SAW propagates over a distance of 0.4 mm. The observed changes are
consistent with results obtained from conventional radio-frequency transmission
measurements, which probe the total SAW absorption due to magnon--phonon
coupling. This result verifies that our method can accurately capture the
spatiotemporal dynamics of a SAW coupled to magnons across the entire length of
the sample. Additionally, we validated our time-resolved profiles by comparing
them with theoretical results that take the echo wave due to reflection into
account. The impact of the echo wave is significant even when it has propagated
over a distance on the order of millimeters. Our imaging results highlight the
visualization of the long-range propagation of the SAW coupled to magnons and
offer more information about the surface vibration profiles in such devices.
