Magnetic excitations and absence of charge order in the van der Waals ferromagnet Fe4.75GeTe2

V. K. Bhartiya; T. Kim; J. Li; T. P. Darlington; D. J. Rizzo; Y. Gu; S. Fan; C. Nelson; J. W. Freeland; X. Xu; D. N. Basov; J. Pelliciari; A. F. May; C. Mazzoli; V. Bisogni

doi:10.1038/s41535-025-00803-1

Magnetic excitations and absence of charge order in the van der Waals ferromagnet Fe_4.75GeTe₂

V. K. Bhartiya, T. Kim, J. Li, T. P. Darlington, D. J. Rizzo, Y. Gu, S. Fan, C. Nelson, J. W. Freeland, X. Xu, D. N. Basov, J. Pelliciari, A. F. May, C. Mazzoli, V. Bisogni

Correlated Electron Materials

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Abstract

Understanding the ground state of van der Waals (vdW) magnets is crucial for designing devices leveraging these platforms. Here, we investigate the magnetic excitations and charge order in Fe_4.75GeTe₂, a vdW ferromagnet with ≈ 315 K Curie temperature. Using Fe L₃-edge resonant inelastic X-ray scattering, we observe a dual nature of magnetic excitations, comprising a coherent magnon and a broad non-dispersive continuum extending up to 150 meV, 50% higher than in Fe_2.72GeTe₂. The continuum intensity is sinusoidally modulated along the stacking direction L, with a period matching the inter-slab distance. Our results indicate that while the dual character of the magnetic excitations is generic to Fe-Ge-Te vdW magnets, Fe_4.75GeTe₂exhibits a longer out-of-plane magnetic correlation length, suggesting enhanced 3D magnetic character. Furthermore, resonant X-ray diffraction reveals that previously reported ±(1/3, 1/3, L) peaks originate from crystal structure rather than from charge order.

Original language	English
Article number	80
Journal	npj Quantum Materials
Volume	10
Issue number	1
DOIs	https://doi.org/10.1038/s41535-025-00803-1
State	Published - Dec 2025

Funding

This work was supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443. Development of Fe4.75GeTe2 crystals (AFM) was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used beamlines 2-ID and 4-ID of NSLS-II, a US DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-SC0012704. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This work was supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443. Development of FeGeTe crystals (AFM) was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used beamlines 2-ID and 4-ID of NSLS-II, a US DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-SC0012704. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. 4.75 2

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Bhartiya, V. K., Kim, T., Li, J., Darlington, T. P., Rizzo, D. J., Gu, Y., Fan, S., Nelson, C., Freeland, J. W., Xu, X., Basov, D. N., Pelliciari, J., May, A. F., Mazzoli, C., & Bisogni, V. (2025). Magnetic excitations and absence of charge order in the van der Waals ferromagnet Fe_4.75GeTe₂. npj Quantum Materials, 10(1), Article 80. https://doi.org/10.1038/s41535-025-00803-1

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title = "Magnetic excitations and absence of charge order in the van der Waals ferromagnet Fe4.75GeTe2",

abstract = "Understanding the ground state of van der Waals (vdW) magnets is crucial for designing devices leveraging these platforms. Here, we investigate the magnetic excitations and charge order in Fe4.75GeTe2, a vdW ferromagnet with ≈ 315 K Curie temperature. Using Fe L3-edge resonant inelastic X-ray scattering, we observe a dual nature of magnetic excitations, comprising a coherent magnon and a broad non-dispersive continuum extending up to 150 meV, 50\% higher than in Fe2.72GeTe2. The continuum intensity is sinusoidally modulated along the stacking direction L, with a period matching the inter-slab distance. Our results indicate that while the dual character of the magnetic excitations is generic to Fe-Ge-Te vdW magnets, Fe4.75GeTe2exhibits a longer out-of-plane magnetic correlation length, suggesting enhanced 3D magnetic character. Furthermore, resonant X-ray diffraction reveals that previously reported ±(1/3, 1/3, L) peaks originate from crystal structure rather than from charge order.",

author = "Bhartiya, \{V. K.\} and T. Kim and J. Li and Darlington, \{T. P.\} and Rizzo, \{D. J.\} and Y. Gu and S. Fan and C. Nelson and Freeland, \{J. W.\} and X. Xu and Basov, \{D. N.\} and J. Pelliciari and May, \{A. F.\} and C. Mazzoli and V. Bisogni",

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AU - Bhartiya, V. K.

AU - Kim, T.

AU - Li, J.

AU - Darlington, T. P.

AU - Rizzo, D. J.

AU - Gu, Y.

AU - Fan, S.

AU - Nelson, C.

AU - Freeland, J. W.

AU - Xu, X.

AU - Basov, D. N.

AU - Pelliciari, J.

AU - May, A. F.

AU - Mazzoli, C.

AU - Bisogni, V.

PY - 2025/12

Y1 - 2025/12

N2 - Understanding the ground state of van der Waals (vdW) magnets is crucial for designing devices leveraging these platforms. Here, we investigate the magnetic excitations and charge order in Fe4.75GeTe2, a vdW ferromagnet with ≈ 315 K Curie temperature. Using Fe L3-edge resonant inelastic X-ray scattering, we observe a dual nature of magnetic excitations, comprising a coherent magnon and a broad non-dispersive continuum extending up to 150 meV, 50% higher than in Fe2.72GeTe2. The continuum intensity is sinusoidally modulated along the stacking direction L, with a period matching the inter-slab distance. Our results indicate that while the dual character of the magnetic excitations is generic to Fe-Ge-Te vdW magnets, Fe4.75GeTe2exhibits a longer out-of-plane magnetic correlation length, suggesting enhanced 3D magnetic character. Furthermore, resonant X-ray diffraction reveals that previously reported ±(1/3, 1/3, L) peaks originate from crystal structure rather than from charge order.

AB - Understanding the ground state of van der Waals (vdW) magnets is crucial for designing devices leveraging these platforms. Here, we investigate the magnetic excitations and charge order in Fe4.75GeTe2, a vdW ferromagnet with ≈ 315 K Curie temperature. Using Fe L3-edge resonant inelastic X-ray scattering, we observe a dual nature of magnetic excitations, comprising a coherent magnon and a broad non-dispersive continuum extending up to 150 meV, 50% higher than in Fe2.72GeTe2. The continuum intensity is sinusoidally modulated along the stacking direction L, with a period matching the inter-slab distance. Our results indicate that while the dual character of the magnetic excitations is generic to Fe-Ge-Te vdW magnets, Fe4.75GeTe2exhibits a longer out-of-plane magnetic correlation length, suggesting enhanced 3D magnetic character. Furthermore, resonant X-ray diffraction reveals that previously reported ±(1/3, 1/3, L) peaks originate from crystal structure rather than from charge order.

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Magnetic excitations and absence of charge order in the van der Waals ferromagnet Fe_4.75GeTe₂

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