  We study the impact of Ga ion exposure on the local and non-local
magnetotransport response in heterostructures of the ferrimagnetic insulator
yttrium iron garnet and platinum. In particular, we cut the yttrium iron garnet
layer in between two electrically separated wires of platinum using a Ga ion
beam, and study the ensuing changes in the magnetoresistive response. We find
that the non-local magnetoresistance signal vanishes when the yttrium iron
garnet film between the Pt wires is fully cut, although the local spin Hall
magnetoresistance signal remains finite. This observation corroborates the
notion that pure spin currents carried by magnons are crucial for the non-local
magnetotransport effects observed in magnetic insulator/metal nanostructures.
