Prediction of Intrinsic Ferromagnetic Ferroelectricity in a Transition-Metal Halide Monolayer

Abstract

The realization of multiferroics in nanostructures, combined with a large electric dipole and ferromagnetic ordering, could lead to new applications, such as high-density multistate data storage. Although multiferroics have been broadly studied for decades, ferromagnetic ferroelectricity is rarely explored, especially in two-dimensional (2D) systems. Here we report the discovery of 2D ferromagnetic ferroelectricity in layered transition-metal halide systems. On the basis of first-principles calculations, we reveal that a charged CrBr_{3} monolayer exhibits in-plane multiferroicity, which is ensured by the combination of orbital and charge ordering as realized by the asymmetric Jahn-Teller distortions of octahedral Cr─Br_{6} units. As an example, we further show that (CrBr_{3})_{2}Li is a ferromagnetic ferroelectric multiferroic. The explored phenomena and mechanism of multiferroics in this 2D system not only are useful for fundamental research in multiferroics but also enable a wide range of applications in nanodevices.

Magnetoelectricity in multiferroics: a theoretical perspective

“…The experience and knowledge learned from three-dimensional magnetoelectric crystals, as reviewed before, can be helpful to search/design low-dimensional multiferroics. For example, the generation of ferroelectricity by noncollinear spin texture has been predicted in Mxene monolayer [114] and the charge-orbital ordering concept has also been implemented in transition-metal halide monolayer to pursuit the ferromagnetic ferroelectricity [115]. Furthermore, the concept of a two-dimensional hyper-ferroelectric metal was proposed [116].…”

Progress and prospects in low‐dimensional multiferroic materials

“…The asymmetric Jahn–Teller distortion of octahedral CrBr 6 units induces in‐plane ferroelectricity coexisting with ferromagnetism in CrBr 3 0.5− . (Reprinted with permission from Reference . Copyright 2018 American Physical Society)…”

Giant pressure-enhancement of multiferroicity in CuBr2

“…First-principles structural and magnetic energy calculations provide a quantitative explanation in terms of dramatically pressure-enhanced interactions between CuBr 2 chains. These large, pressure-tuned magnetic interactions motivate structural control in cuprous halides as a route to applied high-temperature multiferroicity.The search for application-suitable multiferroics [1-3] has advanced significantly over the last decade in both type-I and type-II materials [4][5][6][7][8][9]. Type-I multiferroics [10] have independent magnetic and ferroelectric transitions [11,12], meaning that even when both transition temperatures are high, the magnetoelectric coupling, and hence the scope for mutual control, is usually weak.…”

“…The search for application-suitable multiferroics [1][2][3] has advanced significantly over the last decade in both type-I and type-II materials [4][5][6][7][8][9]. Type-I multiferroics [10] have independent magnetic and ferroelectric transitions [11,12], meaning that even when both transition temperatures are high, the magnetoelectric coupling, and hence the scope for mutual control, is usually weak.…”