Atomic-Scale Visualization of Multiferroicity in Monolayer NiI2

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Advanced Materials, Volume 36, issue 18
Progress in layered van der Waals materials has resulted in the discovery of ferromagnetic and ferroelectric materials down to the monolayer limit. Recently, evidence of the first purely 2D multiferroic material was reported in monolayer NiI2. However, probing multiferroicity with scattering-based and optical bulk techniques is challenging on 2D materials, and experiments on the atomic scale are needed to fully characterize the multiferroic order at the monolayer limit. Here, scanning tunneling microscopy (STM) supported by density functional theory (DFT) calculations is used to probe and characterize the multiferroic order in monolayer NiI2. It is demonstrated that the type-II multiferroic order displayed by NiI2, arising from the combination of a magnetic spin spiral order and a strong spin-orbit coupling, allows probing the multiferroic order in the STM experiments. Moreover, the magnetoelectric coupling of NiI2 is directly probed by external electric field manipulation of the multiferroic domains. The findings establish a novel point of view to analyze magnetoelectric effects at the microscopic level, paving the way toward engineering new multiferroic orders in van der Waals materials and their heterostructures.
Funding Information: M.A. and A.O.F. contributed equally to this work. This research made use of the Aalto Nanomicroscopy Center (Aalto NMC) facilities and was supported by the European Research Council (ERC‐2017‐AdG no. 788185 “Artificial Designer Materials” and ERC‐2021‐StG no. 101039500 “Tailoring Quantum Matter on the Flatland”) and Academy of Finland (Academy professor funding nos. 318995 and 320555, Academy research fellow nos. 331342, 336243 and nos. 338478 and 346654, and Academy postdoctoral fellow no. 349696). Computing resources from the Aalto Science‐IT project and CSC Helsinki are gratefully acknowledged. V.V. acknowledges fellowship support from the Princeton Center for Complex Materials supported by NSF‐DMR‐2011750. | openaire: EC/H2020/788185/EU//E-DESIGN
density-functional theory calculations, magneto electric coupling, multiferroic order, scanning tunneling microscopy, two-dimensional multiferroics
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Amini, M, Fumega, A O, González-Herrero, H, Vaňo, V, Kezilebieke, S, Lado, J L & Liljeroth, P 2024, ' Atomic-Scale Visualization of Multiferroicity in Monolayer NiI 2 ', Advanced Materials, vol. 36, no. 18, 2311342 .