  Proposals for novel spin-orbitronic logic1 and memory devices2 are often
predicated on assumptions as to how materials with large spin-orbit coupling
interact with ferromagnets when in contact. Such interactions give rise to a
host of novel phenomena, such as spin-orbit torques3,4 , chiral
spin-structures5,6 and chiral spin-torques. These chiral properties are related
to the anti-symmetric exchange, also referred to as the interfacial
Dzyaloshinskii-Moriya interaction (DMI)9,10. For numerous phenomena, the
relative strengths of the symmetric Heisenberg exchange and the DMI is of great
importance. Here, we use optical spin-wave spectroscopy (Brillouin light
scattering) to directly determine the DMI vector for a series of Ni80Fe20/Pt
samples, and then compare the nearest-neighbor DMI coupling energy with the
independently measured Heisenberg exchange integral. We find that the
Ni80Fe20-thickness-dependencies of both the microscopic symmetric- and
antisymmetric-exchange are identical, consistent with the notion that the basic
mechanisms of the DMI and Heisenberg exchange essentially share the same
underlying physics, as was originally proposed by Moriya11. While of
significant fundamental importance, this result also leads us to a deeper
understanding of DMI and how it could be optimized for spin-orbitronic
applications.
