Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS
                    <sub>3</sub>
                    ) crystals

Wang, Xingzhi; Du, Ke‐Zhao; Liu, Yu Yang Fredrik; Hu, Peng; Zhang, Jun; Zhang, Qing; Owen, Man Hon Samuel; Lu, Xin; Gan, Chee Kwan; Sengupta, Pinaki; Kloc, Christian; Xiong, Qihua

doi:10.1088/2053-1583/3/3/031009

Cited by 381 publications

(384 citation statements)

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“…Recent Raman studies suggest ferromagnetic ordering in few-layer Cr2Ge2Te6 and antiferromagnetic ordering in monolayer FePS3 28 . However, no evidence yet exists for ferromagnetism persisting down to the monolayer limit.…”

Section: Main Textmentioning

confidence: 99%

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Huang

Clark

Navarro‐Moratalla

et al. 2017

Nature

4,762

179

4,153

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Since the celebrated discovery of graphene 1,2 , the family of two-dimensional (2D) materials has grown to encompass a broad range of electronic properties. Recent additions include spin-valley coupled semiconductors 3 , Ising superconductors 4-6 that can be tuned into a quantum metal 7 , possible Mott insulators with tunable charge-density waves 8 , and topological semi-metals with edge transport 9,10 . Despite this progress, there is still no 2D crystal with intrinsic magnetism [11][12][13][14][15][16] , which would be useful for many technologies such as sensing, information, and data storage 17 . Theoretically, magnetic order is prohibited in the 2D isotropic Heisenberg model at finite temperatures by the Mermin-Wagner theorem 18 . However, magnetic anisotropy removes this restriction and enables, for instance, the occurrence of 2D Ising ferromagnetism. Here, we use magneto-optical Kerr effect (MOKE) microscopy to demonstrate that monolayer chromium triiodide (CrI3) is an Ising ferromagnet with out-of-plane spin orientation. Its Curie temperature of 45 K is only slightly lower than the 61 K of the bulk crystal, consistent with a weak interlayer coupling. Moreover, our studies suggest a layer-dependent magnetic phase transition, showcasing the hallmark thickness-dependent physical properties typical of van der Waals crystals 19-21 . Remarkably, bilayer CrI3 displays suppressed magnetization with a metamagnetic effect 22 , while in trilayer the interlayer ferromagnetism observed in the bulk crystal is restored. Our work creates opportunities for studying magnetism by harnessing the unique features of atomically-thin materials, such as electrical control for realizing magnetoelectronics 13,23 , and van der Waals engineering for novel interface phenomena 17 . 2 Main Text:Magnetic anisotropy is an important requirement for realizing 2D magnetism. In ultrathin metallic films, an easy-axis can originate from symmetry reduction at the interface/surface, which hinges on substrate properties and interface quality [24][25][26] . In contrast, most van der Waals magnets have an intrinsic magnetocrystalline anisotropy due to the reduced crystal symmetry of their layered structures. This offers the coveted possibility to retain a magnetic ground state in the monolayer limit. In addition to studying magnetism in naturally formed crystals in the true 2D limit, layered magnets provide a platform for studying the thickness dependence of magnetism in isolated single crystals where the interaction with the underlying substrate is weak. Namely, the covalently bonded van der Waals layers prevent complex magnetization reorientations induced by epitaxial lattice reconstruction and strain 23 . For layered materials, these advantages come at a low fabrication cost, since the micromechanical exfoliation technique 27 is much simpler than conventional approaches requiring sputtering or sophisticated molecular beam epitaxy.A variety of layered magnetic compounds have recently drawn increased interest due to the possibility of re...

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Section: Main Textmentioning

confidence: 99%

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Huang

Clark

Navarro‐Moratalla

et al. 2017

Nature

4,762

179

4,153

View full text Add to dashboard Cite

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“…Recent advances in this field are putting great pressure on the magnetic memory industry to develop solutions that may remain competitive in speed and data densities against new emerging platforms. Magnetic 2D materials are thus in demand as a possible way forward [17]. Of particular interest for applications in general are 2D crystals and van der Waals heterostructures.…”

mentioning

confidence: 99%

Electrically Controllable Magnetism in Twisted Bilayer Graphene

et al. 2017

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Twisted graphene bilayers develop highly localized states around AA-stacked regions for small twist angles. We show that interaction effects may induce either an antiferromagnetic or a ferromagnetic (FM) polarization of said regions, depending on the electrical bias between layers. Remarkably, FM-polarized AA regions under bias develop spiral magnetic ordering, with a relative 120°misalignment between neighboring regions due to a frustrated antiferromagnetic exchange. This remarkable spiral magnetism emerges naturally without the need of spin-orbit coupling, and competes with the more conventional latticeantiferromagnetic instability, which interestingly develops at smaller bias under weaker interactions than in monolayer graphene, due to Fermi velocity suppression. This rich and electrically controllable magnetism could turn twisted bilayer graphene into an ideal system to study frustrated magnetism in two dimensions. DOI: 10.1103/PhysRevLett.119.107201 Magnetism in 2D electronic systems is known to present a very different phenomenology from its three-dimensional counterpart due to the reduced dimensionality and the increased importance of fluctuations. Striking examples are the impossibility of establishing long range magnetic order in a 2D system without magnetic anisotropy [1] or the emergence of unique finite-temperature phase transitions that are controlled by the proliferation of topological magnetic defects [2]. In the presence of magnetic frustration, in, e.g., Kagome [3,4] or triangular lattices [5][6][7][8], 2D magnetism may also lead to the formation of remarkable quantum spin-liquid phases [3,9,10]. The properties of these states remain under active investigation, and have recently been shown to develop exotic properties, such as fractionalized excitations [11], long-range quantum entanglement of their ground state [12,13], topologically protected transport channels [14], or even high-T C superconductivity upon doping [4,15,16].The importance of 2D magnetism extends also beyond fundamental physics into applied fields. One notable example is data storage technologies. Recent advances in this field are putting great pressure on the magnetic memory industry to develop solutions that may remain competitive in speed and data densities against new emerging platforms. Magnetic 2D materials are thus in demand as a possible way forward [17]. Of particular interest for applications in general are 2D crystals and van der Waals heterostructures. These materials have already demonstrated a great potential for a wide variety of applications, most notably nanoelectronics and optoelectronics [18][19][20]. Some of them have been shown to exhibit considerable tunability through doping, gating, stacking, and strain. Unfortunately, very few 2D crystals have been found to exhibit intrinsic magnetism [21,22], let alone magnetic frustration and potential spin-liquid phases.In this work we predict that twisted graphene bilayers could be a notable exception, realizing a peculiar magnetism on an effective triangular supe...

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“…were identified as van der Waals layered antiferromagnets [23], and they have been revisited recently in light of their potential for studying monolayer materials [24][25][26]. Although antiferromagnetic materials are in some ways less "functional" than ferromagnetic materials, interest in them is growing as ideas for their use as robust spintronic materials develop [27][28][29].…”

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confidence: 99%

Antiferromagnetism in the van der Waals layered spin-lozenge semiconductor CrTe3

McGuire

Garlea

et al. 2017

Phys. Rev. B

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The crystallographic, magnetic, and transport properties of the van der Waals bonded, layered compound CrTe3 have been investigated on single crystal and polycrystalline materials. The crystal structure contains layers made up of lozenge shaped Cr4 tetramers. Electrical resistivity measurements show the crystals to be semiconducting, with a temperature dependence consistent with a band gap of 0.3 eV. The magnetic susceptibility exhibits a broad maximum near 300 K characteristic of low dimensional magnetic systems. Weak anomalies are observed in the susceptibility and heat capacity near 55 K, and single crystal neutron diffraction reveals the onset of long range antiferromagnetic order at this temperature. Strongly dispersive spin-waves are observed in the ordered state. Significant magneto-elastic coupling is indicated by the anomalous temperature dependence of the lattice parameters and is evident in structural optimization in van der Waals density functional theory calculations for different magnetic configurations. The cleavability of the compound is apparent from its handling and is confirmed by first principles calculations, which predict a cleavage energy 0.5 J/m 2 , similar to graphite. Based on these results, CrTe3 is identified as a promising compound for studies of low dimensional magnetism in bulk crystals as well as magnetic order in monolayer materials and van der Waals heterostructures.

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Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS ₃ ) crystals

Abstract: Q. (2016). Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS3) crystals. 2D Materials, 3(3), 031009-.

Cited by 381 publications

References 64 publications

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Electrically Controllable Magnetism in Twisted Bilayer Graphene

Antiferromagnetism in the van der Waals layered spin-lozenge semiconductor CrTe3

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Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS 3 ) crystals

Abstract: Q. (2016). Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS3) crystals. 2D Materials, 3(3), 031009-.

Cited by 381 publications

References 64 publications

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

Electrically Controllable Magnetism in Twisted Bilayer Graphene

Antiferromagnetism in the van der Waals layered spin-lozenge semiconductor CrTe3

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Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS ₃ ) crystals