Multiple spin couplings and layer−valley interactions in room-temperature ferromagnetic Fe₃GaTe₂

Abstract

Fe₃GaTe₂ has attracted significant interest due to its intrinsic room-temperature ferromagnetism, yet its magnetic interactions remain debated. We thoroughly investigate the magnetism of Fe₃GaTe₂ using critical analysis, nitrogen−vacancy (NV) center magnetometry, and Density Function Theory (DFT). Our critical phenomenon analysis with exponents [\beta = 0.3706(9), \gamma = 1.32(6), \delta = 4.7(2)] and DFT calculations reveal competition between itinerant and localized spins driven by anisotropic coupling, which can be attributed to a net charge transfer of approximately 0.22 electrons from Fe³⁺ to surrounding Ge/Te atoms. As confirmed by NV center magnetometry, the ferromagnetism in Fe₃GaTe₂ remains robust even in thin-layered sheet of 16 nm (corresponding to approximately 20 layers). The out-of-plane ferromagnetism in thin Fe₃GaTe₂ sheets is stabilized due to the distinct spin interaction energies between intralayers (J_1 ~ 66.74 meV and J_2 ~ 17.33 meV) and interlayers (J_z ~ 3.78 meV). In addition, the constant energy contour profiles near the Fermi surface of Fe₃GaTe₂ suggest the presence of both hole and electron pockets with a distorted contour around the \mathrm{K}/{\mathrm{K}}^{\mathrm{\prime }} point, indicating hexagonal trigonal warping effects. Furthermore, the layer-resolved electronic band structure uncovers a layer−valley coupling near the Fermi surface, with bands at valleys \mathrm{K} and {\mathrm{K}}^{\mathrm{\prime }} associated with different layers. These findings pave way for advanced electronic applications operating above-room-temperature.

Graphical abstract

Keywords

couplings / layer / interactions / above-room-temperature intrinsic ferromagnetism / strong magnetic anisotropy / critical phenomenon analysis / nitrogen−vacancy (NV) center magnetometry / Density Function Theory (DFT)

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Declarations

The authors declare that they have no competing interests and there are no conflicts.

Electranic Supplementary Material

The online version contains supplementary material available at https://doi.org/10.15302/frontphys.2025.033201. Further details, such as experimental methods, fitting progress, theoretical calculations, and calculated exchange coupling strengths in different possible magnetic configurations, can be found in the supplementary material.

Acknowledgements

This work was supported by the National Key R&D Program of China (Grant No. 2024YFA1611103), the National Natural Science Foundation of China (Grant Nos. 12350410367, 12074360, 12374128, 12074386, 12250410238, and 62150410438), the Alliance of International Science Organizations (Grant Nos. ANSO-VF-2022-03 and ANSO-VF-2024-03), and Anhui Provincial Major S&T Project (Grant No. s202305a12020005). A portion of this work was supported by the Basic Research Program of the Chinese Academy of Sciences Based on Major Scientific Infrastructures (Grant No. JZHKYPT-2021-08) and the High Magnetic Field Laboratory of Anhui Province under Contract No. AHHM-FX-2020-02. We thank the Steady High Magnetic Field Facility (https://cstr.cn/31125.02.SHMFF.XRD) of CAS for data collection and analysis.

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