Direct observation of competition between charge order and itinerant ferromagnetism in the van der Waals crystal 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>5</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>GeTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Wu, Xuchuan; Lei, Le; Yin, Qiangwei; Zhao, Ning-Ning; Li, Man; Wang, Zilu; Liu, Qingxin; Song, Wenhua; Ma, Huan; Ding, Pengfei; Cheng, Zhihai; Li, Kai; Lei, Hechang; Wang, Shancai

doi:10.1103/physrevb.104.165101

Cited by 32 publications

(66 citation statements)

References 49 publications

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“… 10 , 15 , 34 More interestingly, the scanning tunneling microscopy (STM) topography obtained at the surface of Fe 5 GeTe 2 has revealed the existence of 3 1/2 × 3 1/2 superstructures, which are attributed to the ordering of the Fe1 layer. 33 , 35 The intensity of √3 × √3 R 30° reflections is more prominent if a crystal is rapidly quenched. 10 …”

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confidence: 99%

“…Similar to other Fe n GeTe 2 systems, experiments on Fe 5– x GeTe 2 have revealed the presence of Fe deficiency, where x varies from 0.04 15 to 0.28, where Fe1 has the maximum tendency to host a vacancy. 10 , 13 , 33 , 35 We propose a vacancy diffusion model where the swapping of Fe1 can occur via diffusion through different Fe-vacancy sites, as shown in Figure 1 c, where the vacancy sites are marked by hollow circles with the corresponding formation energies E f . Our results verify the fact that the creation of Fe vacancy is most favored at the Fe1 site, as reported by recent experimental studies.…”

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confidence: 99%

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Unusual Magnetic Features in Two-Dimensional Fe₅GeTe₂ Induced by Structural Reconstructions

Ershadrad

Ghosh

Wang

et al. 2022

J. Phys. Chem. Lett.

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Recent experiments on Fe 5 GeTe 2 suggested the presence of a symmetry breaking of its conventional crystal structure. Here, using density functional theory calculations, we elucidate that the stabilization of the (√3 × √3) R 30° supercell structure is caused by the swapping of Fe atoms occurring in the monolayer limit. The swapping to the vicinity of Te atoms is facilitated by the spontaneous occurrence of Fe vacancy and its low diffusion barrier. Our calculated magnetic exchange parameters show the simultaneous presence of ferromagnetic and antiferromagnetic exchange among a particular type of Fe atom. The Fe sublattice projected magnetization obtained from Monte Carlo simulations clearly demonstrates an exotic temperature-dependent behavior of this Fe type along with a large canting angle at T = 0 K, indicating the presence of a complex noncollinear magnetic order. We propose that the low-temperature crystal structure results from the swapping between two sublattices of Fe, giving rise to peculiar magnetization obtained in experiments.

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confidence: 99%

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confidence: 99%

Unusual Magnetic Features in Two-Dimensional Fe₅GeTe₂ Induced by Structural Reconstructions

Ershadrad

Ghosh

Wang

et al. 2022

J. Phys. Chem. Lett.

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“…[35] The existence of a competing charge order above 100 K has also been discussed recently. [18] The magnetic anomaly associated with the formation of magnetic order on the The inset shows the saturation magnetization reached versus nominal arsenic content y (T =2.5 K, H=50 kOe). Antiferromagnetic behavior is observed for the Fe 5 AsTe 2 sample while the mixed As/Ge alloy compositions display ferromagnetic character.…”

Section: Physical Propertiesmentioning

confidence: 99%

“…[13,14,15,16,17] In general, Fe 5−x GeTe 2 and related Fe 4 GeTe 2 have garnered significant attention recently due to their high ordering temperature and complex behaviors. [18,19,20,21,22,23,24,25,26] The present work was motivated by identifying further routes to tune the magnetism in Fe 5−x GeTe 2 and related bulk phases so that novel properties and logical designs of het-erostructures can be achieved.…”

Section: Introductionmentioning

confidence: 99%

“…[5,10] Control over Fe content has not been demonstrated, but the magnetic properties of bulk and thin film Fe 5−x GeTe 2 depend on thermal processing and differences between polycrystalline and single crystalline samples have been observed. [5,6,10,27] Mössbauer spectroscopy has evidenced that spin fluctuations on the (atomically disordered) Fe1 sublattice persist to ≈100 K despite magnetic ordering on the other sublattices near 300 K. [6] Recently, evidence linking magnetic order on the Fe1 sublattice with a competing charge order state has also been discussed, [18] and inversion breaking associated with the atomic (vacancy) ordering on the Fe1(Ge) sublattice has been proposed as a source for helimagnetic order. [23] The ordering of moments on the Fe1 sublattice impacts the electrical properties, the lattice parameters, and the magnetic anisotropy, [6,10] and therefore controlling magnetism on the Fe1 sublattice is essential for tuning the properties of Fe 4.8 GeTe 2 .…”

Section: Introductionmentioning

confidence: 99%

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Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution

May,

Yan,

Hermann

et al. 2021

Preprint

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In order to tune the magnetic properties of the cleavable high-Curie temperature ferromagnet Fe 5−x GeTe 2 , the effect of increasing the electron count through arsenic substitution has been investigated. Small additions of arsenic (2.5 and 5%) seemingly enhance ferromagnetic order in polycrystalline samples by quenching fluctuations on one of the three magnetic sublattices, whereas larger As concentrations decrease the ferromagnetic Curie temperature (T C ) and saturation magnetization. This work also describes the growth and characterization of Fe 4.8 AsTe 2 single crystals that are structurally analogous to Fe 5−x GeTe 2 but with some phase stability complications.Magnetization measurements reveal dominant antiferromagnetic behavior in Fe 4.8 AsTe 2 with a Néel temperature of T N ≈42 K. A field-induced spinflop below T N results in a switch from negative to positive magnetoresistance, with significant hysteresis causing butterfly-shaped resistance loops. In addition to reporting the properties of Fe 4.8 AsTe 2 , this work shows the importance of manipulating the individual magnetic sublattices in Fe 5−x GeTe 2 and motivates further efforts to control the magnetic properties in related materials by fine tuning of the Fermi energy or crystal chemistry.

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Magnetic Anisotropy Control with Curie Temperature above 400 K in a van der Waals Ferromagnet for Spintronic Device

Tang

Huang

et al. 2022

Advanced Materials

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The technological appeal of van der Waals ferromagnetic materials is the ability to control magnetism under external fields with desired thickness toward novel spintronic applications. For practically useful devices, ferromagnetism above room temperature or tunable magnetic anisotropy is highly demanded but remains challenging. To date, only a few layered materials exhibit unambiguous ferromagnetic ordering at room temperature via gating techniques or interface engineering. Here, it is demonstrated that the magnetic anisotropy control and dramatic modulation of Curie temperature (Tc) up to 400 K are realized in layered Fe5GeTe2 via the high‐pressure diamond‐anvil‐cell technique. Magnetic phases manifesting with in‐plane anisotropic, out‐of‐plane anisotropic and nearly isotropic magnetic states can be tuned in a controllable way, depicted by the phase diagram with a maximum Tc up to 360 K. Remarkably, the Tc can be gradually enhanced to above 400 K owing to the Fermi surface evolution during a pressure loading–deloading process. Such an observation sheds light on the understanding and control of emergent magnetic states in practical spintronic applications.

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Direct observation of competition between charge order and itinerant ferromagnetism in the van der Waals crystal Fe5−xGeTe2

Cited by 32 publications

References 49 publications

Unusual Magnetic Features in Two-Dimensional Fe₅GeTe₂ Induced by Structural Reconstructions

Unusual Magnetic Features in Two-Dimensional Fe₅GeTe₂ Induced by Structural Reconstructions

Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution

Magnetic Anisotropy Control with Curie Temperature above 400 K in a van der Waals Ferromagnet for Spintronic Device

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Direct observation of competition between charge order and itinerant ferromagnetism in the van der Waals crystal Fe5−xGeTe2

Cited by 32 publications

References 49 publications

Unusual Magnetic Features in Two-Dimensional Fe5GeTe2 Induced by Structural Reconstructions

Unusual Magnetic Features in Two-Dimensional Fe5GeTe2 Induced by Structural Reconstructions

Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution

Magnetic Anisotropy Control with Curie Temperature above 400 K in a van der Waals Ferromagnet for Spintronic Device

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Product

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Unusual Magnetic Features in Two-Dimensional Fe₅GeTe₂ Induced by Structural Reconstructions

Unusual Magnetic Features in Two-Dimensional Fe₅GeTe₂ Induced by Structural Reconstructions