Wafer-scale two-dimensional ferromagnetic Fe3GeTe2 thin films grown by molecular beam epitaxy

Liu, Shanshan; Yuan, Xiang; Zou, Yichao; Shen, Yu; Huang, Ce; Zhang, Enze; Ling, Jiwei; Liu, Yanwen; Wang, Weiyi; Zhang, Cheng; Zou, Jin; Wang, Kaiyou; Xiu, Faxian

doi:10.1038/s41699-017-0033-3

Cited by 199 publications

(203 citation statements)

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“…Currently a good dozen 2D magnetic crystals have been studied, either obtained by exfoliating 3D parent layered magnets (see Box 1) or by growing them directly on a substrate [50][51][52] . Due to the limited space available, it is impossible to review all of them here, and we will focus on the two most studied systems -CrI3 and Fe3GeTe2.…”

Section: From Bulk To 2d Magnetism Theoretical Considerationmentioning

confidence: 99%

“…Unlike CrI3, Fe3GeTe2 is a metal with carrier concentration that has been reported to vary from 1.2×10 19 cm -3 in samples grown by molecular beam epitaxy 51 (with a carrier mobility of ~50 cm 2 /V·s) to ~10 21 cm -3 (approximately 8×10 13 cm -2 per layer) in crystals grown using the chemical vapour transport method 79 . Alongside Kerr measurements, the anomalous Hall effect has been used to study magnetism 51 . Micromechanical cleavage of this material is difficult using conventional methods and, in order to increase the chances to obtain monolayer flakes, exfoliation was performed on freshly-evaporated gold 55 or on Al2O3 59 .…”

Section: Fe 3 Getementioning

confidence: 99%

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Magnetic 2D materials and heterostructures

et al. 2019

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The family of 2D materials grows day by day, drastically expanding the scope of possible phenomena to be explored in two dimensions, as well as the possible van der Waals heterostructures that one can create. Such 2D materials currently cover a vast range of properties. Until recently, this family has been missing one crucial member -2D magnets. The situation has changed over the last two years with the introduction of a variety of atomically-thin magnetic crystals. Here we will discuss the difference between magnetic states in 2D materials and in bulk crystals and present an overview of the 2D magnets that have been explored recently. We will focus, in particular, on the case of the two most studied systems -semiconducting CrI3 and metallic Fe3GeTe2 -and illustrate the physical phenomena that have been observed. Special attention will be given to the range of novel van der Waals heterostructures that became possible with the appearance of 2D magnets, offering new perspectives in this rapidly expanding field.

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Section: From Bulk To 2d Magnetism Theoretical Considerationmentioning

confidence: 99%

Section: Fe 3 Getementioning

confidence: 99%

Magnetic 2D materials and heterostructures

et al. 2019

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“…FM has been found in Fe 3 GeTe 2 below 230 K . Fe 3 GeTe 2 monolayer has been prepared by molecular beam epitaxy (MBE) and found to be FM with T c ≈ 216 K …”

Section: Potential 2d Phase‐transition Materialsmentioning

confidence: 99%

Potential 2D Materials with Phase Transitions: Structure, Synthesis, and Device Applications

et al. 2018

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bandgap can overcome the short channel effect, and then can scale down transistors to sub-10 nm [13,14] and even sub-5 nm [10,[15][16][17][18] to extend the Moore's law. Over last decades, typical 2D semiconductors, such as MoS 2 and WSe 2 , have been intensively studied. [19][20][21][22] On the other hand, 2D materials with versatile phase-transition properties offer new opportunities in both fundamental research and future device applications. In the last few years, a lot of exciting experiments have been conducted on this subfamily of 2D materials in the monolayer limit, such as charge density wave (CDW) 1T-TaS 2 , [23][24][25][26] superconducting (SC) 2H-NbSe 2 , [27][28][29] ferromagnetic (FM) CrI 3 , [12,30,31] and Cr 2 Ge 2 Te 6 . [11,32] CDW is a phenomenon of forming a standing-wave-like electron density usually accompanied with a lattice distortion and a bandgap opening due to electronphonon interaction. [33] SC is a phenomenon of zero electrical resistance and expulsion of magnetic flux fields also originated from electron-phonon interaction. [34] Magnetism and electric polarization stem from spontaneous spin/dipole ordering, respectively. [35,36] Parallel and antiparallel spins constitute long-range ferromagnetic (FM) and antiferromagnetic (AFM) ordering, respectively. Similarly, parallel and antiparallel dipoles form ferroelectric (FE) and antiferroelectric (AFE) ordering, respectively. Van der Waals layered materials can show a lot of novel properties, especially in the atomic thickness limit. This includes the follow ing terms: (1) The odd/even layer effect may emerge due to weak interlayer coupling. For example, FM or FE ordering may appear in the odd layers, while AFM or AFE ordering may appear in the even layers; (2) Due to confinement effect in the out-of-plane direction, new ordering structures may appear;(3) The properties can be easily tuned by strain, external fields, interface interaction, and so on. Toward fundamental property measurement and device applications, the challenge remains, such as predicting/discovering new 2D phase-transition materials, controlling the chemical synthesis, overcoming the poor air stability, and so on. Here, a literature survey has been carried out to search possible 2D phase-transition materials. Recent progress on the chemical synthesis and property investigation of some obtained monolayers has been reviewed, including CDW 1T-TaS 2 monolayers, FM CrI 3 mono layers, and so on.Layered materials with phase transitions, such as charge density wave (CDW) and magnetic and dipole ordering, have potential to be exfoliated into monolayers and few-layers and then become a large and important subfamily of two-dimensional (2D) materials. Benefitting from enriched physical properties from the collective interactions, long-range ordering, and related phase transitions, as well as the atomic thickness yet having nondangling bonds on the surface, 2D phase-transition materials have vast potential for use in new-concept and functional devices. Here, potential 2D phase-transit...

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“…Fe 5−x GeTe 2 , sometimes referred to as Fe 5 GeTe 2 , has recently emerged as an interesting vdW material. 6,7 This phase is unique from Fe 3−x GeTe 2 , [8][9][10][11][12][13][14][15] which has been studied as a vdW ferromagnet that can be exfoliated to the monolayer limit. 16,17 In the bulk, Fe 5−x GeTe 2 has a higher Curie temperature (260-310 K) than Fe 3−x GeTe 2 (150-240 K).…”

Section: Introductionmentioning

confidence: 99%

Physical properties and thermal stability of Fe5−xGeTe2 single crystals

May

Bridges

McGuire

2019

Phys. Rev. Materials

132

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The magnetic and transport properties of Fe-deficient Fe5GeTe2 single crystals (Fe5−xGeTe2 with x ≈0.3) were studied and the impact of thermal processing was explored. Quenching crystals from the growth temperature has been previously shown to produce a metastable state that undergoes a strongly hysteretic first-order transition upon cooling below ≈ 100 K. The first-order transition impacts the magnetic properties, yielding an enhancement in the Curie temperature TC from 270 to 310 K. In the present work, THT ≈550 K has been identified as the temperature above which metastable crystals are obtained via quenching. Diffraction experiments reveal a structural change at this temperature, and significant stacking disorder occurs when samples are slowly cooled through this T range. The transport properties are demonstrated to be similar regardless of the crystal's thermal history. The scattering of charge carriers appears to be dominated by moments fluctuating on the Fe(1) sublattice, which remain dynamic down to ≈ 100-120 K. Maxima in the magnetoresistance and anomalous Hall resistance are observed near 120 K. The Hall and Seebeck coefficients are also impacted by magnetic ordering on the Fe(1) sublattice. The data suggest that both electrons and holes contribute to conduction above 120 K, but that electrons dominate at lower T when all of the Fe sublattices are magnetically ordered. This study demonstrates a strong coupling of the magnetism and transport properties in Fe5−xGeTe2 and complements the previous results that demonstrated strong magnetoelastic coupling as the Fe(1) moments order. The published version of this manuscript is

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Wafer-scale two-dimensional ferromagnetic Fe3GeTe2 thin films grown by molecular beam epitaxy

Cited by 199 publications

References 50 publications

Magnetic 2D materials and heterostructures

Magnetic 2D materials and heterostructures

Potential 2D Materials with Phase Transitions: Structure, Synthesis, and Device Applications

Physical properties and thermal stability of Fe5−xGeTe2 single crystals

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