Charge carrier densities in electronic heterostructures are typically responsive to external electric fields or chemical doping but rarely to their magnetization history. Here, we demonstrate that magnetization acts as a non-volatile control parameter for the density of states in bilayer graphene (BLG) interfaced with the antiferromagnetic insulator chromium oxychloride (COC). Using capacitance measurements, we observe a hysteretic behavior in the density of states of BLG on a COC substrate in response to an external magnetic field, which is unrelated to the history of electrostatic gating. First-principles calculations revealed that such hysteresis arises from the magnetic-field-controlled charge transfer between BLG and COC during the antiferromagnetic (AFM) to ferrimagnetic-like (FiM) state phase transition of COC. Our work demonstrates that interfacial charging states can be effectively controlled magnetically, and it also shows that capacitance measurement is a suitable technique for detecting subtle changes not detectable via conventional resistivity measurements. These findings broaden the scope of proximity effects and open new possibilities for nanoelectronics applications.
The generation of pseudo-magnetic fields in strained graphene leads to quantized Landau levels in the absence of an external magnetic field, providing the potential to achieve a zero-magnetic-field analogue of quantum Hall effect. Here, we report the realization of pseudo-magnetic field in epitaxial graphene by building monolayer CrCl2/graphene heterointerface. The CrCl2 crystal structure exhibits spontaneous breaking of three-fold rotational symmetry, yielding anisotropic displacement field at the interface. Using scanning tunneling spectroscopy, we have discovered a sequence of pseudo-Landau levels associated with massless Dirac fermions. A control experiment performed on CrCl2/NbSe2 interface confirms the origin as the pseudo-magnetic field in the graphene layer that strongly interacts with the CrCl2. More interestingly, the strength of the pseudo-magnetic fields can be tuned by the twist angle between the monolayer CrCl2 and graphene, with a variation of up to threefold, depending on the twist angle of 0° to 30°. This work presents a rare 2D heterojunction for exploring PMF-related physics, such as valley Hall effect, with the advantage of easy and flexible implementation.
Yangliu Wu, Zhaozhuo Zeng, Haipeng Lu, Xiaocang Han, Chendi Yang, Nanshu Liu, Xiaoxu Zhao, Liang Qiao, Wei Ji*, Renchao Che, Longjiang Deng*, Peng Yan* and Bo Peng*
Abstract:
Multiferroic materials have been intensively pursued to achieve the mutual control of electric and magnetic properties. The breakthrough progress in 2D magnets and ferroelectrics encourages the exploration of low-dimensional multiferroics, which holds the promise of understanding inscrutable magnetoelectric coupling and inventing advanced spintronic devices. However, confirming ferroelectricity with optical techniques is challenging in 2D materials, particularly in conjunction with antiferromagnetic orders in single- and few-layer multiferroics. Here, we report the discovery of 2D vdW multiferroic with out-of plane ferroelectric polarization in trilayer NiI2 device, as revealed by scanning reflective magnetic circular dichroism microscopy and ferroelectric hysteresis loops. The evolution between ferroelectric and antiferroelectric phases has been unambiguously observed. Moreover, the magnetoelectric interaction is directly probed by magnetic control of the multiferroic domain switching. This work opens up opportunities for exploring new multiferroic orders and multiferroic physics at the limit of single or few atomic layers, and for creating advanced magnetoelectronic devices.
Realizing magnetic skyrmions in two-dimensional (2D) van der Waals (vdW) ferromagnets offers unparalleled prospects for future spintronic applications. The room-temperature ferromagnet Fe3GaTe2 provides an ideal platform for tailoring these magnetic solitons. Here, skyrmions of distinct topological charges are artificially introduced and spatially engineered using magnetic force microscopy (MFM). The skyrmion lattice is realized by specific field-cooling process, and can be further controllably erased and painted via delicate manipulation of tip stray field. The skyrmion lattice with opposite topological charges (S = +1 or -1) can be tailored at the target regions to form topological skyrmion junctions (TSJs) with specific configurations. The delicate interplay of TSJs and spin-polarized device current were finally investigated via the in-situ transport measurements, alongside the topological stability of TSJs. Our results demonstrate that Fe3GaTe2 not only serves as a potential building block for room-temperature skyrmion-based spintronic devices, but also presents promising prospects for Fe3GaTe2-based heterostructures with the engineered topological spin textures.
