Proximity effects in graphene/chromia heterostructures*

Chromia is an insulating magneto-electric, exhibiting antiferromagnetic character in bulk up to an elevated Neel temperature of 307 K. The magneto-electric nature of the chromia allows the direction of the net magnetism at this surface to be reversed electrically, by application of an appropriate voltage in the simultaneous presence of magnetic field and with low power dissipation. As a substrate, chromia offers room-temperature control of proximity effects in graphene, in marked contrast to previously reported ferromagnetic insulators. In this study, we have investigated the signatures of spin transport in heterostructures formed from CVD-graphene and chromia (Cr₂O₃). The non-local resistance measured in spin Hall geometry shows a maximum as the gate voltage is swept through the Dirac point. This spin-Hall signal is shown to persist beyond the Neel temperature of 307 K, and to persist instead all the way up to 350 K. This suggests that the signal is driven by strong spin-orbit coupling between the 2D layer and the chromia. These results are a step towards all-electric access to spin polarized currents at room temperature in graphene/Cr₂O₃ heterostructures, making them a highly promising system for future antiferromagnetic spintronic applications.