Room-temperature in-plane ferromagnetism in Co-substituted Fe5GeTe2 investigated by magnetic x-ray spectroscopy and microscopy

Emily Heppell; Ryuji Fujita; Gautam Gurung; Jheng Cyuan Lin; Andrew F. May; Michael Foerster; M. Waqas Khaliq; Miguel Angel Niño; Manuel Valvidares; Javier Herrero-Martín; Pierluigi Gargiani; Kenji Watanabe; Takashi Taniguchi; Dirk Backes; Gerrit van der Laan; Thorsten Hesjedal

doi:10.1088/2053-1583/ada040

Room-temperature in-plane ferromagnetism in Co-substituted Fe₅GeTe₂ investigated by magnetic x-ray spectroscopy and microscopy

Emily Heppell, Ryuji Fujita, Gautam Gurung, Jheng Cyuan Lin, Andrew F. May, Michael Foerster, M. Waqas Khaliq, Miguel Angel Niño, Manuel Valvidares, Javier Herrero-Martín, Pierluigi Gargiani, Kenji Watanabe, Takashi Taniguchi, Dirk Backes, Gerrit van der Laan, Thorsten Hesjedal

Correlated Electron Materials

Research output: Contribution to journal › Article › peer-review

Abstract

The exploration of two-dimensional (2D) van der Waals ferromagnets has revealed intriguing magnetic properties with significant potential for spintronics applications. In this study, we examine the magnetic properties of Co-doped Fe₅GeTe₂ using x-ray photoemission electron microscopy (XPEEM) and x-ray magnetic circular dichroism (XMCD), complemented by density functional theory calculations. Our XPEEM measurements reveal that the Curie temperature ( T C ) of a bilayer of (Co_xFe 1 − x ) 5 − δ GeTe₂ (with x = 0.28) reaches ∼300 K—a notable enhancement over most 2D ferromagnets in the ultrathin limit. Interestingly, the T C shows only a small dependence on film thickness (bulk T C ≈ 340 K), in line with the observed in-plane (IP) magnetic anisotropy and robust IP exchange coupling. XMCD measurements indicate that the spin moments for both Fe and Co are significantly reduced compared to the theoretical values. These insights highlight the potential of Co-doped Fe₅GeTe₂ for stable, high-temperature ferromagnetic applications in 2D materials.

Original language	English
Article number	025001
Journal	2D Materials
Volume	12
Issue number	2
DOIs	https://doi.org/10.1088/2053-1583/ada040
State	Published - Apr 2025

Funding

The XMCD experiments were performed at the BOREAS beamline, and the XPEEM experiments at the CIRCE beamline, both at the ALBA Synchrotron under proposals 2023027573 and 2022097164, respectively. E H acknowledges a STFC-Diamond-EPSRC studentship (2604894, EP/R513295/1, EP/T517811/1). K W and T T acknowledge support from the JSPS KAKENHI (Grant Numbers 21H05233 and 23H02052) and World Premier International Research Center Initiative (WPI), MEXT, Japan. R F and T H acknowledge financial support from the Oxford-ShanghaiTech collaboration project. R F, T H, and G L were supported by the Engineering and Physical Sciences Research Council under Grants EP/X015556/1 and EP/X015599/1, respectively. We thank Diamond Light Source for access to the facilities of the Materials Characterisation Laboratory. Bulk crystal synthesis and characterization (A.F.M.) were supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Keywords

(CoFe)GeTe
2D van der Waals magnets
XPEEM
ferromagnetism
x-ray absorption spectroscopy
x-ray magnetic circular dichroism

Access to Document

10.1088/2053-1583/ada040

Cite this

Heppell, E., Fujita, R., Gurung, G., Lin, J. C., May, A. F., Foerster, M., Waqas Khaliq, M., Angel Niño, M., Valvidares, M., Herrero-Martín, J., Gargiani, P., Watanabe, K., Taniguchi, T., Backes, D., van der Laan, G., & Hesjedal, T. (2025). Room-temperature in-plane ferromagnetism in Co-substituted Fe₅GeTe₂ investigated by magnetic x-ray spectroscopy and microscopy. 2D Materials, 12(2), Article 025001. https://doi.org/10.1088/2053-1583/ada040

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title = "Room-temperature in-plane ferromagnetism in Co-substituted Fe5GeTe2 investigated by magnetic x-ray spectroscopy and microscopy",

abstract = "The exploration of two-dimensional (2D) van der Waals ferromagnets has revealed intriguing magnetic properties with significant potential for spintronics applications. In this study, we examine the magnetic properties of Co-doped Fe5GeTe2 using x-ray photoemission electron microscopy (XPEEM) and x-ray magnetic circular dichroism (XMCD), complemented by density functional theory calculations. Our XPEEM measurements reveal that the Curie temperature ( T C ) of a bilayer of (CoxFe 1 − x ) 5 − δ GeTe2 (with x = 0.28) reaches ∼300 K—a notable enhancement over most 2D ferromagnets in the ultrathin limit. Interestingly, the T C shows only a small dependence on film thickness (bulk T C ≈ 340 K), in line with the observed in-plane (IP) magnetic anisotropy and robust IP exchange coupling. XMCD measurements indicate that the spin moments for both Fe and Co are significantly reduced compared to the theoretical values. These insights highlight the potential of Co-doped Fe5GeTe2 for stable, high-temperature ferromagnetic applications in 2D materials.",

keywords = "(CoFe)GeTe, 2D van der Waals magnets, XPEEM, ferromagnetism, x-ray absorption spectroscopy, x-ray magnetic circular dichroism",

author = "Emily Heppell and Ryuji Fujita and Gautam Gurung and Lin, {Jheng Cyuan} and May, {Andrew F.} and Michael Foerster and {Waqas Khaliq}, M. and {Angel Ni{\~n}o}, Miguel and Manuel Valvidares and Javier Herrero-Mart{\'i}n and Pierluigi Gargiani and Kenji Watanabe and Takashi Taniguchi and Dirk Backes and {van der Laan}, Gerrit and Thorsten Hesjedal",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Published by IOP Publishing Ltd.",

year = "2025",

month = apr,

doi = "10.1088/2053-1583/ada040",

language = "English",

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Heppell, E, Fujita, R, Gurung, G, Lin, JC, May, AF, Foerster, M, Waqas Khaliq, M, Angel Niño, M, Valvidares, M, Herrero-Martín, J, Gargiani, P, Watanabe, K, Taniguchi, T, Backes, D, van der Laan, G & Hesjedal, T 2025, 'Room-temperature in-plane ferromagnetism in Co-substituted Fe₅GeTe₂ investigated by magnetic x-ray spectroscopy and microscopy', 2D Materials, vol. 12, no. 2, 025001. https://doi.org/10.1088/2053-1583/ada040

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T1 - Room-temperature in-plane ferromagnetism in Co-substituted Fe5GeTe2 investigated by magnetic x-ray spectroscopy and microscopy

AU - Heppell, Emily

AU - Fujita, Ryuji

AU - Gurung, Gautam

AU - Lin, Jheng Cyuan

AU - May, Andrew F.

AU - Foerster, Michael

AU - Waqas Khaliq, M.

AU - Angel Niño, Miguel

AU - Valvidares, Manuel

AU - Herrero-Martín, Javier

AU - Gargiani, Pierluigi

AU - Watanabe, Kenji

AU - Taniguchi, Takashi

AU - Backes, Dirk

AU - van der Laan, Gerrit

AU - Hesjedal, Thorsten

PY - 2025/4

Y1 - 2025/4

N2 - The exploration of two-dimensional (2D) van der Waals ferromagnets has revealed intriguing magnetic properties with significant potential for spintronics applications. In this study, we examine the magnetic properties of Co-doped Fe5GeTe2 using x-ray photoemission electron microscopy (XPEEM) and x-ray magnetic circular dichroism (XMCD), complemented by density functional theory calculations. Our XPEEM measurements reveal that the Curie temperature ( T C ) of a bilayer of (CoxFe 1 − x ) 5 − δ GeTe2 (with x = 0.28) reaches ∼300 K—a notable enhancement over most 2D ferromagnets in the ultrathin limit. Interestingly, the T C shows only a small dependence on film thickness (bulk T C ≈ 340 K), in line with the observed in-plane (IP) magnetic anisotropy and robust IP exchange coupling. XMCD measurements indicate that the spin moments for both Fe and Co are significantly reduced compared to the theoretical values. These insights highlight the potential of Co-doped Fe5GeTe2 for stable, high-temperature ferromagnetic applications in 2D materials.

AB - The exploration of two-dimensional (2D) van der Waals ferromagnets has revealed intriguing magnetic properties with significant potential for spintronics applications. In this study, we examine the magnetic properties of Co-doped Fe5GeTe2 using x-ray photoemission electron microscopy (XPEEM) and x-ray magnetic circular dichroism (XMCD), complemented by density functional theory calculations. Our XPEEM measurements reveal that the Curie temperature ( T C ) of a bilayer of (CoxFe 1 − x ) 5 − δ GeTe2 (with x = 0.28) reaches ∼300 K—a notable enhancement over most 2D ferromagnets in the ultrathin limit. Interestingly, the T C shows only a small dependence on film thickness (bulk T C ≈ 340 K), in line with the observed in-plane (IP) magnetic anisotropy and robust IP exchange coupling. XMCD measurements indicate that the spin moments for both Fe and Co are significantly reduced compared to the theoretical values. These insights highlight the potential of Co-doped Fe5GeTe2 for stable, high-temperature ferromagnetic applications in 2D materials.

KW - (CoFe)GeTe

KW - 2D van der Waals magnets

KW - XPEEM

KW - ferromagnetism

KW - x-ray absorption spectroscopy

KW - x-ray magnetic circular dichroism

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U2 - 10.1088/2053-1583/ada040

DO - 10.1088/2053-1583/ada040

M3 - Article

AN - SCOPUS:85214296362

SN - 2053-1583

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JO - 2D Materials

JF - 2D Materials

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