Determining the Proximity Effect Induced Magnetic Moment in Graphene by Polarised Neutron Reflectivity and X-ray Magnetic Circular Dichroism

R. O. M. Aboljadayel, D. M. Love, C. A. F. Vaz, R. S. Weatherup, P. Braeuninger-Weimer, M. -B. Martin, A. Cabrero-Vilatela, A. Ionescu, C. J. Kinane, T. R. Charlton, J. Llandro, P. M. S. Monteiro, C. H. W. Barnes, S. Hofmann, S. Langridge

Published 2021-01-25Version 1

We report the magnitude of the induced magnetic moment in CVD-grown epitaxial and rotated-domain graphene as a result of the proximity effect in the vicinity of the ferromagnetic substrates Co and Ni, using polarised neutron reflectivity (PNR). Although rotated-domain graphene is known to interact weakly with the ferromagnetic underlayer in comparison with the epitaxial graphene, the PNR results indicate an induced magnetic moment of $\sim$ 0.57 $\mu_\textrm{B}$/C atom at 10 K for both structures. The origin of the induced magnetic moment is found to be due to the opening of the graphene's Dirac cone as a result of the strong C $p_z-3d$ hybridisation, which was confirmed by additional PNR measurements using a non-magnetic Ni$_9$Mo$_1$ and Cu substrates. We validated our PNR fitting models using the Bayesian uncertainty analysis and corroborated the results by X-ray magnetic circular dichroism measurements.