Magnetic Proximity Effect in Graphene/CrBr₃ van der Waals Heterostructures

Abstract

the third method, that is, the introduction of magnetism in graphene with the proximity effect in the interface of magnetic insulators and graphene. Pioneer works have been demonstrated with 3D bulk magnetic insulators like yttrium iron garnet, europium (II) sulfide, and bismuth ferrite. [7][8][9][10][11][12][13][14][15] Due to the short-range nature of the magnetic exchange coupling, a fully 2D van der Waals heterostructures is desired for downsizing the device and introducing magnetic proximity effect (MPE) at the same time. The recent profound discoveries of 2D ferromagnets [16][17][18][19][20][21][22][23][24][25][26][27][28][29] bring the possibility of 2D ferromagnetic van der Waals heterostructures, [30][31][32][33][34][35][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. Furthermore, we observe anomalous longitudinal resistance changes at the Dirac point R XX,D with increasing external magnetic field near ν = 0. This may attribute to the MPE induced ground state phases transformation of graphene from the ferromagnetic state at the lower magnetic field and a canted antiferromagnetic state at a higher field in quantum Hall regime.A typical graphene/CrBr 3 van der Waals heterostructure with Hall bar structure for electrical transport measurement is fabricated as shown in Figure 1a. In order to reach the best performance and a substantial MPE in graphene/CrBr 3 heterostructures, we optimize the fabrication process and conditions to achieve the desired heterostructures (see Experimental Section for details). The sample in the final stage is encapsulated and protected by poly(methyl methacrylate) (PMMA), which keeps the device surface away from the moisture and air for cryotemperature tests. The atomic structure of layered CrBr 3 is shown in Figure 1b. The Cr 3+ ions are configured in a honeycomb network, and the green arrows represent the spin direction of Cr atoms, which are found to exhibit a strong ferromagnetic coupling. [39][40][41][42][43][44] The Raman spectra of Figure 1c indicates that the monolayer graphene still preserves a high crystal quality when heterostructured with CrBr 3 layer. The optical image in 2D van der Waals heterostructures serve as a promising platform to exploit various physical phenomena in a diverse range of novel spintronic device applications. Efficient spin injection is the prerequisite for these devices. The recent discovery of magnetic 2D materials leads to the possibility of fully 2D van der Waals spintronics devices by implemen...

Recent Advances in 2D Materials for Photodetectors

“…[ 68 ] Recently, Tang et al. [ 69 ] investigated magnetic proximity effect between graphene/CrBr 3 heterojunction. Similarly, this magnetic proximity effect in monolayer WSe 2 and trilayer CrI 3 heterostructure was also discovered by Zhong et al.…”

Spin-induced negative thermal expansion and spin–phonon coupling in van der Waals material CrBr3

“…In the few-layer forms of CrX 3 and heterostructures containing these materials a number of emerging phenomena, including electric field and stacking-dependent control of magnetism, giant tunneling magnetoresistance, giant nonreciprocal second harmonics generation, magnetic proximity effect, important for development of broad range spintronic devices, was observed [11][12][13][14][15][16][17] . These phenomena arise from a complex interplay of various degrees of freedom associated with the charge carriers and atomic layers.…”

van der Waals Magnets: Material Family, Detection and Modulation of Magnetism, and Perspective in Spintronics

“…Reproduced with permission. [ 171 ] Copyright 2020, Wiley‐VCH. e) Field‐dependent nonlocal Hanle spin precession measurements for the graphene proximitized with CrGeTe 3 at different temperatures.…”