Strong intrinsic room-temperature ferromagnetism in freestanding non-van der Waals ultrathin 2D crystals

Hao Wu,Juan Du,Jie Li,Haixin Chang,Luying Li,Yihua Gao,Jun Wang,Liang Zhang,Haibo Shu,Wenfeng Zhang,Li Yang

doi:10.1038/s41467-021-26009-0

Abstract

Control of ferromagnetism is of critical importance for a variety of proposed spintronic and topological quantum technologies. Inducing long-range ferromagnetic order in ultrathin 2D crystals will provide more functional possibility to combine their unique electronic, optical and mechanical properties to develop new multifunctional coupled applications. Recently discovered intrinsic 2D ferromagnetic crystals such as Cr2Ge2Te6, CrI3 and Fe3GeTe2 are intrinsically ferromagnetic only below room temperature, mostly far below room temperature (Curie temperature, ~20–207 K). Here we develop a scalable method to prepare freestanding non-van der Waals ultrathin 2D crystals down to mono- and few unit cells (UC) and report unexpected strong, intrinsic, ambient-air-robust, room-temperature ferromagnetism with TC up to ~367 K in freestanding non-van der Waals 2D CrTe crystals. Freestanding 2D CrTe crystals show comparable or better ferromagnetic properties to widely-used Fe, Co, Ni and BaFe12O19, promising as new platforms for room-temperature intrinsically-ferromagnetic 2D crystals and integrated 2D devices.

Highlights

Control of ferromagnetism is of critical importance for a variety of proposed spintronic and topological quantum technologies
Recent efforts to explore the ferromagnetism in ultrathin 2D crystals have revealed intrinsic ferromagnetism in mechanically exfoliated Cr2Ge2Te6, CrI3, and Fe3GeTe2 few-layer crystals, but the ferromagnetic ordering only exists significantly far below room temperature[2,3,4,5,6,7,8,9]
BaFe12O19 (Fig. 3g–i and Supplementary Table 1, more discussions in notes for Supplementary Table 1)[24]. These results indicate that freestanding nonvan der Waals 2D crystals provide a new route to obtain and tune the intrinsic room-temperature 2D ferromagnetism in 2D

Summary

Introduction

Control of ferromagnetism is of critical importance for a variety of proposed spintronic and topological quantum technologies. We develop a scalable method to prepare freestanding non-van der Waals ultrathin 2D crystals down to mono- and few unit cells (UC) and report unexpected strong, intrinsic, ambient-air-robust, room-temperature ferromagnetism with TC up to ~367 K in freestanding non-van der Waals 2D CrTe crystals. Recent efforts to explore the ferromagnetism in ultrathin 2D crystals have revealed intrinsic ferromagnetism in mechanically exfoliated Cr2Ge2Te6, CrI3, and Fe3GeTe2 few-layer crystals, but the ferromagnetic ordering only exists significantly far below room temperature[2,3,4,5,6,7,8,9]. Considering the difficulty to mechanically exfoliate non-van der Waals crystals using tape, here we develop a CVD-assisted ultrasonication method to obtain ultrathin freestanding non-van der Waals 2D CrTe crystals with thickness down to mono-unit cells (UC), few-UC, and multi-UC.

Methods

Results

Conclusion