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

By Bevin Huang, Genevieve Clark, E. Navarro-Moratalla, Dahlia R. Klein, R. Cheng, K. Seyler, Ding Zhong, E. Schmidgall, M. McGuire, D. Cobden and 4 more. Nature, 2017

5,109 citations recorded by the source corpus.

Since the discovery of graphene, the family of two-dimensional materials has grown, displaying a broad range of electronic properties. Recent additions include semiconductors with spin–valley coupling, Ising superconductors that can be tuned into a quantum metal, possible Mott insulators with tunable charge-density waves, and topological semimetals with edge transport. However, no two-dimensional crystal with intrinsic magnetism has yet been discovered; such a crystal would be useful in many technologies from sensing to data storage. Theoretically, magnetic order is prohibited in the two-dimensional isotropic Heisenberg model at finite temperatures by the Mermin–Wagner theorem. Magnetic anisotropy removes this restriction, however, and enables, for instance, the occurrence of two-dimensional Ising ferromagnetism. Here we use magneto-optical Kerr effect microscopy to demonstrate that monolayer chromium triiodide (CrI3) is an Ising ferromagnet with out-of-plane spin orientation. Its Curie temperature of 45 kelvin is only slightly lower than that of the bulk crystal, 61 kelvin, which is consistent with a weak interlayer coupling. Moreover, our studies suggest a layer-dependent magnetic phase, highlighting thickness-dependent physical properties typical of van der Waals crystals. Remarkably, bilayer CrI3 displays suppressed magnetization with a metamagnetic effect, whereas in trilayer CrI3 the interlayer ferromagnetism observed in the bulk crystal is restored. This work creates opportunities for studying magnetism by harnessing the unusual features of atomically thin materials, such as electrical control for realizing magnetoelectronics, and van der Waals engineering to produce interface phenomena.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/abedf9ed6c4d4dcba4f65a3a8acab82ae5343d9e

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Citations in the corpus

Colloquium : Spintronics in graphene and other two-dimensional materials (2019, methodology): “12(b), layer dependent magnetic ordering in CrI3 was demonstrated down to monolayer thickness, with its spins constrained to lie vertical to the lattice plane as described by the Ising model (Huang et al., 2017).”
A perspective on conventional high-temperature superconductors at high pressure: Methods and materials (2019, background): “The successful synthesis of a plethora of two-dimensional systems over the last years such as transition metal dichalcogenides [526], layered transition metal oxides [527, 528], hexagonal-boron nitride [529], topological insulators [530], 2D-cuprates [531], ferromagnetic 2D systems [532], phosphoren”
Antiferromagnetic ordering in van der Waals 2D magnetic material MnPS3 probed by Raman spectroscopy (2019, methodology): “Moreover, because antiferromagnetic phases do not have net magnetization, a direct measurement of antiferromagnetic ordering using a tool such as magneto-optical Kerr effect (MOKE), which is otherwise useful in the case of atomically-thin ferromagnetic materials, is not possible, either [10,11].”
Interplay between Kitaev interaction and single ion anisotropy in ferromagnetic CrI3 and CrGeTe3 monolayers (2018, background): “(4) and (5) but also explains the previously determined Ising behavior of CrI3 favoring the outof-plane direction for the magnetization.(1,5,12) In the case of CrGeTe3, the b parameter is also found to be negative and leads to bK adopting a negative −0.”
Gapless Surface Dirac Cone in Antiferromagnetic Topological Insulator MnBi2Te4 (2019, background): “While layered AFM insulators like CrI3 fulfill the magnetic structure but lack a nonzero topological invariant [15], a novel family of van der Waals layered single crystalline materials MnBi2nTe3nþ1 (n 1⁄4 1; 2;.”