  Converting angular momentum between different degrees of freedom within a
magnetic material results from a dynamic interplay between electrons, magnons
and phonons. This interplay is pivotal to implementing spintronic device
concepts that rely on spin angular momentum transport. We establish a new
concept for long-range angular momentum transport that further allows to
address and isolate the magnonic contribution to angular momentum transport in
a nanostructured metallic ferromagnet. To this end, we electrically excite and
detect spin transport between two parallel and electrically insulated
ferromagnetic metal strips on top of a diamagnetic substrate. Charge-to-spin
current conversion within the ferromagnetic strip generates electronic spin
angular momentum that is transferred to magnons via electron-magnon coupling.
We observe a finite angular momentum flow to the second ferromagnetic strip
across a diamagnetic substrate over micron distances, which is electrically
detected in the second strip by the inverse charge-to-spin current conversion
process. We discuss phononic and dipolar interactions as the likely cause to
transfer angular momentum between the two strips. Moreover, our work provides
the experimental basis to separate the electronic and magnonic spin transport
and thereby paves the way towards magnonic device concepts that do not rely on
magnetic insulators.
