Yanfeng Zhang's group and collaborators have made important progress in the controllable preparation and magnetic properties of novel self-inserting phase iron selenide nanomaterials

Recently, Professor Zhang Yanfeng's research group and his collaborators from the School of Materials Science and Engineering of Peking University prepared a new iron selenide nanomaterial with iron self-inserting layer structure by chemical vapor deposition, and obtained two-dimensional iron selenide materials with room temperature ferromagnetic properties by adjusting the proportion of iron intercalation, and the related work was published in Advanced Materials
.

Two-dimensional magnetic materials can maintain long-range magnetic order in monoprotocell thickness and are easily regulated by external fields, which will undoubtedly provide an ideal material system for the study of magnetism and other novel physical properties under two-dimensional limits, and also provide candidate materials
for the development of low-power spintronics/magnetic storage devices.
Related research is also a frontier hotspot in the field of two-dimensional materials research
.

However, the magnetic characteristics of the discovered two-dimensional magnetic materials (including transition metal halides, transition metal germanium tellurium compounds, etc.
) can only be presented in a low temperature environment, and have high environmental sensitivity, which is easy to chemically react with water and oxygen in the air, which greatly limits their magnetic research and practical application exploration
.
Therefore, the development of new two-dimensional magnetic materials with high magnetic transition temperature and good environmental stability is a key problem
that needs to be solved urgently.

In recent years, researchers have found that the interlayers of two-dimensional layered transition metal chalcogenides (TMDCs) can insert transition metal atoms, occupy octahedral vacancies in the van der Waals gap and form covalent bonds to form a new type of self-inserting layered TMDCs material
.
Previously prepared partially self-inserted phase TMDCs materials (such as_{Cr 2S3}, V₅S₈) can exhibit ferromagnetic or antiferromagnetic properties, but their magnetic transition temperature is still much lower than room temperature
.

By precisely regulating the chemical potential of each component in the chemical vapor deposition reaction path, Yanfeng Zhang's team and collaborators realized the controllable preparation of iron selenide (25% iron-embeddedtriclinic Fe5Se₈ and 50% iron-embedded monoclinic Fe3Se4) nanomaterials with different intercalation ratios.
It was found that the proportion and occupancy of intercalated Fe atoms had a significant effect
on the physical properties of iron selenide in the intercalated phase.
Among them, Fe₅Se 8 exhibits intrinsic room temperature ferromagnetic properties and good environmental stability, and DFT theoretical calculations reveal that the introduction of intercalated Fe atoms changes the spin state density of intrinsically non-magnetic layered 1T'-_FeSe2, so that the total spin density in the triclinic phase_Fe5Se₈ is transferred from intercalated Fe atoms to Fe atoms in the layer
。 Fe3_Se4, on the other hand, exhibits metallic properties and has high conductivity when the nanosheet thickness is less than 10 nm, which is expected to be used as an electrode material
in two-dimensional transistor devices.

Crystal structure and basic physical properties of triclinic_Fe5Se₈ and monoclinic_Fe3Se₄

This study not only provides a new method for the controllable preparation of two-dimensional intercalated TMDCs materials, but also discovers a new strategy to control the basic physical properties (from non-magnetic to magnetic) of two-dimensional TMDCs materials by changing the proportion of intercalated metal atoms, and provides new research ideas
for the exploration of new two-dimensional magnetic materials and other functional materials.

Yahuan Huang, a postdoctoral fellow in Zhang Yanfeng's research group, Luo Tiantian, a doctoral student in the research group of Associate Professor Zheng Feipeng of Jinan University, and Han Xiaozang, a postdoctoral fellow in the research group of Zhao Xiaoxuan of Peking University, are the co-first authors of the paper, and Zhang Yanfeng, Professor Wang Jian of Peking University and Associate Professor Wang Lili of Tsinghua University are the co-corresponding authors
of the paper.
The above work has been supported
by the National Natural Science Foundation of China, the Key R&D Program of the Ministry of Science and Technology, the State Key Laboratory of Low-dimensional Quantum Physics Open Research Fund, the China Postdoctoral Science Foundation, the Guangdong Basic and Applied Basic Research Fund, and the Guangzhou Science and Technology Program.
The theoretical computing part was completed
in the high-performance computing cluster of Jinan University and the Tianhe supercomputer system.

Paper Information:

Composition-Controllable Syntheses and Property Modulations from 2D Ferromagnetic Fe₅Se₈to Metallic Fe₃Se ₄Nanosheets

Yahuan Huan,Tiantian Luo,Xiaocang Han,Jun Ge,Fangfang Cui,Lijie Zhu,Jingyi Hu,Feipeng Zheng,Xiaoxu Zhao,Lili Wang*,Jian Wang*,Yanfeng Zhang*

Adv.
Mater.
,https://doi.
org/10.
1002/adma.
202207276