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

TL;DR

This study quantifies the magnetic moments induced in graphene when in proximity to ferromagnetic nickel, using polarized neutron reflectivity and X-ray magnetic circular dichroism, revealing a significant magnetic polarization due to hybridization effects.

Contribution

The paper provides the first quantitative measurement of proximity-induced magnetic moments in graphene using PNR and XMCD, highlighting the role of C pz-3d hybridization.

Findings

Induced magnetic moment in graphene up to 0.53 μB/C atom at 10 K

Magnetic moments depend on graphene's growth orientation

No magnetic moment observed on non-magnetic Ni9Mo1 substrate

Abstract

We report the magnitude of the induced magnetic moment in CVD-grown epitaxial and rotated-domain graphene in proximity with a ferromagnetic Ni film, using polarized neutron reflectivity (PNR) and X-ray magnetic circular dichroism (XMCD). The XMCD spectra at the C K-edge confirms the presence of a magnetic signal in the graphene layer and the sum rules give a magnetic moment of up to $\sim\,0.47\,\mu$_B/C atom induced in the graphene layer. For a more precise estimation, we conducted PNR measurements. The PNR results indicate an induced magnetic moment of $\sim$ 0.53 $\mu$_B/C atom at 10 K for rotated graphene and $\sim$ 0.38 $\mu$_B/C atom at 10 K for epitaxial graphene. Additional PNR measurements on graphene grown on a non-magnetic Ni_9Mo_1 substrate, where no magnetic moment in graphene is measured, suggest that the origin of the induced magnetic moment is due to the opening of the graphene's Dirac cone as a result of the strong C pz-3d hybridization.