Room‐Temperature Magnetoelectric Coupling in Atomically Thin ε‐Fe₂O₃

Abstract

coupling in multiferroics has attracted considerable research interests due to the wide range of applications in high-density information storages and low-energyconsumption spintronic devices. [7][8][9][10][11][12][13][14] Notably, the manipulation of magnetism by electric field has shown the transformative potential in the next-generation logic devices. [15][16][17][18][19][20][21][22][23][24] Nevertheless, the magnetoelectric coupling is extremely weak in traditional type-I multiferroics because of the mutually exclusive origins between ferroelectricity and ferromagnetism. In this context, searching for new types of multiferroics, especially at 2D community, is of great significance.Monolayer Hf 2 VC 2 F 2 was predicted to be a type-II multiferroic with a high phase transition temperature. [25] The ferroelectric polarization was induced by a unique 120° Y-type antiferromagnetic structure and was modulated by the magnetic field, nevertheless, it was difficult to achieve the electrically controlled magnetism. The sliding ferroelectricity was observed in bilayer VS 2 , [26] however, the environmental stability of atomically thin VS 2 was unsatisfactory. Ultrathin-layered CuCrS 2 and CuCrSe 2 were room-temperature multiferroics, and the ferromagnetism was stabilized by the enhanced carrier density and the vertical polarization-induced orbital shifting. [27,28] 2D multiferroics with magnetoelectric coupling combine the magnetic order and electric polarization in a single phase, providing a cornerstone for constructing high-density information storages and low-energy-consumption spintronic devices. The strong interactions between various order parameters are crucial for realizing such multifunctional applications, nevertheless, this criterion is rarely met in classical 2D materials at room-temperature. Here an ingenious space-confined chemical vapor deposition strategy is designed to synthesize atomically thin non-layered ε-Fe 2 O 3 single crystals and disclose the room-temperature long-range ferrimagnetic order. Interestingly, the strong ferroelectricity and its switching behavior are unambiguously discovered in atomically thin ε-Fe 2 O 3 , accompanied with an anomalous thicknessdependent coercive voltage. More significantly, the robust room-temperature magnetoelectric coupling is uncovered by controlling the magnetism with electric field and verifies the multiferroic feature of atomically thin ε-Fe 2 O 3 . This work not only represents a substantial leap in terms of the controllable synthesis of 2D multiferroics with robust magnetoelectric coupling, but also provides a crucial step toward the practical applications in low-energy-consumption electric-writing/magnetic-reading devices.

Highly Sensitive Long‐Wave Infrared Photodetector Based on Two‐Dimensional Hematite α‐Fe2O3

“…Recently, a 2D 𝜖-Fe 2 O 3 nanoflake was prepared using the chemical vapor deposition (CVD) method and demonstrated roomtemperature magnetoelectric coupling. [33] Herein, we report the synthesis of well-defined hexagonal phase 2D 𝛼-Fe 2 O 3 nanoflakes via the CVD method. The 2D hexagonal 𝛼-Fe 2 O 3 nanoflake photodetector demonstrated wide spectral photoresponse from visible to the LWIR.…”

Tuning 2D Magnetism in Cobalt Monoxide Nanosheets Via In Situ Nickel‐Doping

“…2D magnetic metal oxides promise exciting technological opportunities for exploring magnetism down to atomic‐layer thickness. Instances of recent success include iron oxides, [ 10–12 ] spinel‐type, and perovskite‐type [ 13–15 ] metal oxides. [ 16,17 ] Balan et al.…”

“…demonstrated the coexistence of the ferrimagnetic order and electric polarization in an atomically thin ε ‐Fe 2 O 3 . [ 12 ] Cheng et al. reported the synthesis of 2D cobalt ferrite nanosheets via van der Waals epitaxy strategy.…”

“…2D magnetic metal oxides promise exciting technological opportunities for exploring magnetism down to atomic-layer thickness. Instances of recent success include iron oxides, [10][11][12] spinel-type, and perovskitetype [13][14][15] metal oxides. [16,17] Balan et al demonstrated the fabrication of 2D 𝛼-Fe 2 O 3 by liquid exfoliation, which exhibits ferromagnetic ordering with a good degree of saturation.…”

“…[11] Wang et al demonstrated the coexistence of the ferrimagnetic order and electric polarization in an atomically thin 𝜖-Fe 2 O 3 . [12] Cheng et al reported the synthesis of 2D cobalt ferrite nanosheets via van der Waals epitaxy strategy. [13] The asgrown samples exhibit long-range ferrimagnetic order and semiconducting nature within thickness down to 2 nm.…”