One Million Percent Tunnel Magnetoresistance in a Magnetic van der Waals Heterostructure

Kim, Hyun Ho; Yang, Bowen; Patel, Τ. C.; Sfigakis, F.; Li, Chenghe; Tian, Shangjie; Lei, Hechang; Tsen, Adam W.

doi:10.1021/acs.nanolett.8b01552

Cited by 253 publications

(272 citation statements)

References 45 publications

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“…S1 for the optical image of the device.) Before applying pressure, G shows a jump at the spin-flip transition field ≈ 0.75 T. This is the spin-filtering effect that has been recently reported in few-layer CrI3 (ref [16][17][18][19][20]. The electron tunneling rate is higher when spins are aligned with the magnetization of each CrI3 layer.…”

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confidence: 56%

Pressure-controlled interlayer magnetism in atomically thin CrI3

et al. 2019

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These authors contributed equally: Tingxin Li, Shengwei Jiang.Stacking order can significantly influence the physical properties of two-dimensional (2D) van der Waals materials 1 . The recent isolation of atomically thin magnetic materials 2-22 opens the door for control and design of magnetism via stacking order. Here we apply hydrostatic pressure up to 2 GPa to modify the stacking order in a prototype van der Waals magnetic insulator CrI3. We observe an irreversible interlayer antiferromagnetic (AF) to ferromagnetic (FM) transition in atomically thin CrI3 by magnetic circular dichroism and electron tunneling measurements. The effect is accompanied by a monoclinic to a rhombohedral stacking order change characterized by polarized Raman spectroscopy. Before the structural change, the interlayer AF coupling energy can be tuned up by nearly 100% by pressure. Our experiment reveals interlayer FM coupling, which is the established ground state in bulk CrI3, but never observed in native exfoliated thin films. The observed correlation between the magnetic ground state and the stacking order is in good agreement with first principles calculations 23-27 and suggests a route towards nanoscale magnetic textures by moiré engineering 28 .Intrinsic magnetism in 2D van der Waals materials has received growing attention 2-22 . Of particular interest is the thickness-dependent magnetic ground state in atomically thin CrI3. In these exfoliated thin films, the magnetic moments are aligned (in the out-of-plane direction) in each layer, but anti-aligned in adjacent layers 3,12-22 . They are FM (or AF) depending on whether there is (or isn't) an uncompensated layer. The relatively weak interlayer coupling compared to the intralayer coupling allows effective ways to control the interlayer magnetism, which have led to interesting spintronics applications including voltage switching 12-14 , spin filtering 16-20 and spin transistors 21 . The origin of interlayer AF coupling is, however, not well understood since interlayer FM order is the ground state in the bulk crystals. Recent ab initio calculations 23-27 and experiments 22,29,30 have suggested that stacking order could provide an explanation but a direct correlation between stacking order and interlayer magnetism is lacking.In bulk CrI3, the Cr atoms in each layer form a honeycomb structure, and each Cr atom is surrounded by six I atoms in an octahedral coordination (Fig. 1a). The bulk crystals undergo a structural phase transition from a monoclinic phase (space group C2/m) at room temperature to a

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confidence: 56%

Pressure-controlled interlayer magnetism in atomically thin CrI3

et al. 2019

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“…The behaviour observed is typical of a very soft ferromagnet, with the formation of magnetic domains causing the remnant magnetization to vanish and the absence of magnetic hysteresis. Clear evidence for a second magnetic phase transition at T ~ 50K is found in low-field magnetization measurements with B applied parallel to the layers, but neither its nature nor the details of the ensuing magnetic state are currently understood 72 . This is worth pointing out, because this second transition appears to be related to the unexpected behaviour observed in atomically thin crystals (see below).…”

Section: From Bulk To 2d Magnetism Theoretical Considerationmentioning

confidence: 99%

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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“…Moreover, in the limit ε F ∆ the only non-vanishing contributions to Gilbert dampings are given by the first terms on the right-hand sides of Eqs. (20) that are manifestly anisotropic.…”

Section: Gilbert Dampingmentioning

confidence: 99%

“…The results of Eqs. (20), (21) suggest that the anisotropy of Gilbert damping is most pronounced in the metal limit, ε F ∆ + λ as far as λτ / 1. In particular, certain spin density responses are vanishing in this limit.…”

Section: Qualitative Considerationmentioning

confidence: 99%

Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

et al. 2020

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Giant Gilbert damping anisotropy is identified as a signature of strong Rashba spin-orbit coupling in a two-dimensional antiferromagnet on a honeycomb lattice. The phenomenon originates in spinorbit induced splitting of conduction electron subbands that strongly suppresses certain spin-flip processes. As a result, the spin-orbit interaction is shown to support an undamped non-equilibrium dynamical mode that corresponds to an ultrafast in-plane Néel vector precession and a constant perpendicular-to-the-plane magnetization. The phenomenon is illustrated on the basis of a two dimensional s-d like model. Spin-orbit torques and conductivity are also computed microscopically for this model. Unlike Gilbert damping these quantities are shown to reveal only a weak anisotropy that is limited to the semiconductor regime corresponding to the Fermi energy staying in a close vicinity of antiferromagnetic gap. arXiv:1911.03408v1 [cond-mat.str-el]

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One Million Percent Tunnel Magnetoresistance in a Magnetic van der Waals Heterostructure

Cited by 253 publications

References 45 publications

Pressure-controlled interlayer magnetism in atomically thin CrI3

Pressure-controlled interlayer magnetism in atomically thin CrI3

Magnetic 2D materials and heterostructures

Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

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