Proximity effects in graphene and ferromagnetic CrBr₃ van der Waals heterostructures

Abstract

Schematic of the magnetic proximity effect in a van der Waals heterostructure formed by a graphene monolayer, induced by its interaction with a two-dimensional ferromagnet (CrBr3) for designing a single-gate field effect transistor.

Magnetic Proximity Effect in Graphene/CrBr3 van der Waals Heterostructures

“…The recent profound discoveries of 2D ferromagnets [ 16–29 ] bring the possibility of 2D ferromagnetic van der Waals heterostructures, [ 30–36 ] it is urgent and essential to comprehensively investigate the magnetic coupling between graphene and 2D ferromagnetic materials for developing 2D spintronic devices. Not just the evidence of the existence of MPE in 2D ferromagnetic van der Waals heterostructures, [ 37,38 ] here, we report the direct observation of MPE in graphene/CrBr 3 van der Waals heterostructures by probing Zeeman spin Hall effect (ZSHE) through non‐local transport measurements. A further quantitative estimation of Zeeman splitting field demonstrates a significant magnetic proximity exchange field even in a low magnetic field.…”

“…Moreover, other possible source of producing non‐local signal like ohmic contribution were analyzed and excluded (Figure S5, Supporting Information). As to the finite V nl at 0 T, it may be due to the spin Hall effect caused by spin polarization which is induced by the exchange field under 0 T, [ 13,37 ] since the magnetic hysteresis of 2D CrBr 3 [ 44 ] and EuS [ 52 ] is different, CrBr 3 has a non‐zero remanence but EuS is zero at zero applied field (Text S6 and Table S1, Supporting Information). Therefore, this feature enables the prospect of utilizing novel devices without external magnetic field which cannot be generated on nano spatial scales.…”

“…In addition, the origin of MPE at the interface of graphene/CrBr 3 van der Waals heterostructures can be explained by a recent first‐principle calculated model on the MPE in 2D graphene/CrBr 3 heterostructure. [ 37 ] MPE which is strongly dependent on the orbital hybridization at the interface, arises from the spin dependent interlayer coupling and results in the overall spin polarization to 63.6% in the heterostructure system by calculating its electronic structure of the graphene/CrBr 3 heterolayer, and a further perpendicular gating electric field can tune the miniband spin splitting. The theoretical predications agree with the observation of a large non‐zero spin hall effect signal at zero field in this work due to spin polarization in graphene/CrBr 3 heterostructure.…”

Electrical and thermal generation of spin currents by magnetic bilayer graphene

“…In this regard, graphene is a superior choice with its high charge carrier mobility as the absence of hyperfine interactions and small intrinsic spin-orbit coupling (SOC) allow for a long spin lifetime [9][10][11] . The proximity of other materials to graphene can efficiently modulate its band structure and induce considerable SOC 12,13 and exchange interaction [14][15][16][17][18] , which are essential for spin generation and manipulation. In particular, the proximity effect of 2D magnetic materials would bring the technology of ultrathin spin-logic devices to the limit when the magnetic behaviour of an individual atomic layer directly controls the long-distance information transfer by the spins in the neighbouring graphene layer.…”

Elucidating proximity magnetism through polarized neutron reflectometry and machine learning

“…This opens up the possibility of realizing emergent phenomena such as the quantum anomalous Hall effect [43][44][45][46][47] or axion insulator state [48][49][50] at room temperature and advancing TI-based device applications. More recently, the realization of proximity magnetism in van der Waals heterostructures [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] presents new opportunities to engineer atomically thin devices with novel functionalities, and at the same time highlights an increasing need for precise characterization of interfacial effects at subnanometer length scales. Thus, accurate quantitative analysis of magnetic structural information obtained by PNR is critical to resolving important interfacial effects within a broad range of materials systems.…”