Free-standing 2D non-van der Waals antiferromagnetic hexagonal FeSe semiconductor: halide-assisted chemical synthesis and Fe2+ related magnetic transitions

Junjie Xu; Wei Li; Biao Zhang; Liang Zha; Wei Hao; Shixin Hu; Jinbo Yang; ShuZhou Li; Song Gao; Yanglong Hou

doi:10.1039/d1sc04122c

Free-standing 2D non-van der Waals antiferromagnetic hexagonal FeSe semiconductor: halide-assisted chemical synthesis and Fe²⁺ related magnetic transitions

Chem Sci. 2021 Dec 1;13(1):203-209. doi: 10.1039/d1sc04122c. eCollection 2021 Dec 22.

Authors

Junjie Xu¹, Wei Li¹, Biao Zhang¹, Liang Zha², Wei Hao³, Shixin Hu⁴, Jinbo Yang², ShuZhou Li³, Song Gao^{5

6}, Yanglong Hou¹

Affiliations

¹ Beijing Key Laboratory of Magnetoelectric Materials and Devices, School of Materials Science and Engineering, Beijing Innovation Centre for Engineering Science and Advanced Technology, Peking University Beijing 100871 China hou@pku.edu.cn.
² State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University Beijing 100871 China.
³ School of Materials Science and Engineering, Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore.
⁴ Institute of Applied Magnetics, Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University Lanzhou 730000 China.
⁵ Beijing Key Laboratory for Magnetoelectric Materials and Devices, College of Chemistry and Molecular Engineering, Peking University Beijing 100871 China.
⁶ Institute of Spin-X Science and Technology, South China University of Technology Guangzhou 511442 China.

Abstract

The scarcity of two-dimensional (2D) magnetic nanostructures has hindered their applications in spintronics, which is attributed to that most magnetic materials exhibit non-van der Waals (nvdWs) structures and it is hard to reduce their thickness to 2D nanostructures. Thus it is necessary to develop a promising strategy for free-standing 2D magnetic nvdWs nanostructures. We have achieved free-standing 2D nvdWs hexagonal FeSe with a thickness of 2.9 nm by the reaction between the oleylamine-Se complex and Fe²⁺ with the assistance of Cl^-, where the synergetic effects of Cl^- and -NH₂ lead to anisotropic growth. Inspiringly, the 2D hexagonal FeSe exhibits intrinsic antiferromagnetic order rooted in Fe²⁺ and semiconducting nature. In addition, the temperature variation would result in the chemical environment changes of Fe²⁺, responsible for the temperature-dependent magnetic transitions. This work promotes the potential applications of 2D hexagonal FeSe and the preparation of other 2D nvdWs materials.