Magnon junction effect in Y3Fe5O12/CoO/Y3Fe5O12 insulating heterostructures

Magnonics as an emerging frontier of spintronics aims using magnons to deliver information free from electron scattering and as-induced Joule heating. In general, magnon currents can be excited both thermally and electrically in magnetic insulators by applying a current in an adjacent heavy-metal layer. Here, we report another kind of magnon junctions (MJs) composed of Y3Fe5O12/CoO/ Y3Fe5O12 heterostructures, in which Y3Fe5O12 and CoO are, respectively, ferrimagnetic and antiferromagnetic insulators. A temperature gradient can drive a high (low) magnon current via the spin Seebeck effect when the Y3Fe5O12 layers in an MJ are configured at the parallel (antiparallel) state, showing a spin valve-like behavior. Electrically injected magnon current could also be controlled by the MJs, contributing to a magnon-mediate nonlocal spin Hall magnetoresistance (SMR). Furthermore, compared with its NiO counterpart, both the magnon junction and magnon-mediate SMR effects can be clearly observed at room temperature for the CoO-based magnon junctions, which can possibly be applied as a building block for room-temperature magnon-based memory or logic devices.