Microscopic origin of multiferroic order in monolayer NiI2

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Abstract

The discovery of multiferroic behavior in monolayer NiI2 provides a new symmetry-broken state in van der Waals monolayers, featuring the simultaneous emergence of helimagnetic order and ferroelectric order at a critical temperature of T = 21 K. However, the microscopic origin of multiferroic order in NiI2 monolayer has not been established, and in particular, the role of non-collinear magnetism and spin–orbit coupling in this compound remains an open problem. Here we reveal the origin of the two-dimensional multiferroicity in NiI2 using first-principles electronic structure methods. We show that the helimagnetic state appears as a consequence of the long-range magnetic exchange interactions, featuring sizable magnetic moments in the iodine atoms. We demonstrate that the electronic density reconstruction accounting for the ferroelectric order emerges from the interplay of non-collinear magnetism and spin–orbit coupling. We demonstrate that the ferroelectric order is controlled by the iodine spin–orbit coupling, and leads to an associated electronically-driven distortion in the lattice. Our results establish the microscopic origin of the multiferroic behavior in monolayer NiI2, putting forward the coexistence of helical magnetic order and ligand spin–orbit coupling as driving forces for multiferroic behavior in two-dimensional materials.
Original languageEnglish
Article number025010
Pages (from-to)1-7
Number of pages7
Journal2D Materials
Volume9
Issue number2
DOIs
Publication statusPublished - 1 Apr 2022
MoE publication typeA1 Journal article-refereed

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  • -: Lado Jose AT-palkka

    Lado, J.

    01/09/202031/08/2025

    Project: Academy of Finland: Other research funding

  • -: Lado Jose AT-kulut

    Lado, J., Hyart, T., Kumar, P. & Koch, R.

    01/09/202031/08/2023

    Project: Academy of Finland: Other research funding

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