  In magnetic multilayer systems, a large spin-orbit coupling at the interface
between heavy metals and ferromagnets can lead to intriguing phenomena such as
the perpendicular magnetic anisotropy, the spin Hall effect, the Rashba effect,
and especially the interfacial Dzyaloshinskii-Moriya (IDM) interaction. This
interfacial nature of IDM interaction has been recently revisited because of
its scientific and technological potential. Here, we demonstrate an
experimental technique to straightforwardly observe the IDM interaction, namely
Brillouin light scattering. The non-reciprocal spin wave dispersions,
systematically measured by Brillouin light scattering, allow not only the
determination of the IDM energy densities beyond the regime of perpendicular
magnetization but also the revelation of the inverse proportionality with the
thickness of the magnetic layer, which is a clear signature of the interfacial
nature. All together, our experimental and theoretical approaches involving
double time Green,s function methods open up possibilities for exploring
magnetic hybrid structures for engineering the IDM interaction.
