Nature communications”width =” “height =” “/> The figure shows the van der Waals (vdW) heterostructure of G / FL-CrI3 / Gr (G: graphene, FL: some layers, CrI3: chromium (III) iodide, Gr: graphite) used in the microscopy study tunnel effect (STM). (a) The schematic illustration and (b) the optical image of the experimental set-up. The sample consists of monolayer graphene covering the FL-CrI3 stack on graphite flakes (G / FL-CrI3 / Gr). (c) The atomic structure of the CrI3 monolayer (top view). The bias-dependent STM images of G / FL-CrI3 / Gr show the (d) graphene lattice – taken at Vs = -0.3 V and (e) the CrI3 network – taken at Vs = 2.5 V with the superimposed atomic structure of the CrI3 monolayer (I atoms of the lower atomic plane are deleted for clarity). Credit: Nature Communication
Scientists at NUS have demonstrated a general approach to characterize the atomic structure and electronic and magnetic properties of two-dimensional (2-D) magnetic insulators using scanning tunneling microscopy.
The recent discovery of 2D magnets and the development of van der Waals (vdW) heterostructure engineering provide unprecedented opportunities not only to explore the exciting physics of magnetism in reduced dimensions, but also to develop new spintronic devices. generation for quantum technology applications. Further developments in this field involve understanding at the atomic level of the electronic and magnetic properties of 2D magnets and their heterostructures. Unfortunately, the direct application of conventional tunneling microscopy (STM) techniques to learn more about material properties does not work well for 2D magnetic insulators. STM imaging relies on the quantum tunneling effect, whereby electrons pass from the atomically sharp tip to conductive samples or vice versa. It does not apply to the study of massive insulating materials because there is no conductive path.
A NUS research team led by Professor Jiong Lu of the Department of Chemistry, NUS demonstrated the application of STM to study the antiferromagnetic insulating chromium (III) iodide (CrI3) crystals by incorporating them with vdW graphene-based heterostructures (see figure). This work is in collaboration with Professor Kostya S. Novoselov of the Department of Materials Science and Engineering, NUS. Their technique extends the capabilities of the STM by allowing it to study insulating materials to better understand the magnetic order in 2D magnets.
By capping the material under study with a single layer of graphene, the research team is able to achieve the stacking order and inter-layer magnetic coupling of the exfoliated CrI.3 which is a few layers thick using STM imaging under low temperature conditions. They also identified the magnetic structure and demonstrated that STM imaging can distinguish between ferromagnetic and antiferromagnetic structures of CrI.3 (a few thick layers). This is due to the special interaction of the magnetic states with the superimposed graphene.
Professor Lu said, “Our approach is general in nature and represents a breakthrough. in the field of atomic-scale characterization of atomic structure, electronic and magnetic properties of various magnetic insulators and their vdW heterostructures. It can facilitate the development of 2D magnetic isolators for new generation spintronic devices
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Zhizhan Qiu et al. Visualization of the atomic structure and magnetism of 2D magnetic insulators via a tunnel through graphene, Nature Communication (2021). DOI: 10.1038 / s41467-020-20376-w
Quote: Visualize the Atomic Structure and Magnetism of 2-D Magnetic Insulators (2021, February 3) retrieved December 8, 2021 from https://phys.org/news/2021-02-visualising-atomic-magnetism-d-magnetic. html
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