Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures

Abstract

We study the impact of Ga ion exposure on the local and nonlocal 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 nonlocal 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 nonlocal magnetotransport effects observed in magnetic insulator/metal nanostructures, while possible transport processes through the substrate can be ruled out.