Probing magnetism in atomically thin semiconducting PtSe2

Abstract

Atomic-scale disorder in two-dimensional transition metal dichalcogenides is often accompanied by local magnetic moments, which can conceivably induce long-range magnetic ordering into intrinsically non-magnetic materials. Here, we demonstrate the signature of long-range magnetic orderings in defective mono- and bi-layer semiconducting PtSe2 by performing magnetoresistance measurements under both lateral and vertical measurement configurations. As the material is thinned down from bi- to mono-layer thickness, we observe a ferromagnetic-to-antiferromagnetic crossover, a behavior which is opposite to the one observed in the prototypical 2D magnet CrI3. Our first-principles calculations, supported by aberration-corrected transmission electron microscopy imaging of point defects, associate this transition to the interplay between the defect-induced magnetism and the interlayer interactions in PtSe2. Furthermore, we show that graphene can be effectively used to probe the magnetization of adjacent semiconducting PtSe2. Our findings in an ultimately scaled monolayer system lay the foundation for atom-by-atom engineering of magnetism in otherwise non-magnetic 2D materials.

Two‐dimensional magnetic transition metal chalcogenides

“…Extrinsic magnetism can be also introduced into the otherwise nonmagnetic 2D TMCs by proximity coupling, 30 defects, 31,32 doping, 33,34 and so on. Elegant examples include the long‐rang magnetic ordering induced by Pt vacancies in ultrathin PtSe 2 films, 35,36 and V‐dopants in ML WSe 2 37,38 . These results inspire further research interest in the study of 2D magnetic TMCs.…”

“…Thickness‐modulated magnetism in ultrathin PtSe 2 crystals induced by Pt vacancies has been recently demonstrated by Kis' group via magnetoresistance measurements (Figure 6). 35,36 PtSe 2 is an interesting TMC material due to its unique thickness‐dependent electronic properties and undergoes a metal‐to‐semiconductor transition from thin films (e.g., > 4 nm) to few‐layer films (<2.5 nm) 89 . Figure 6A shows the AFM image of the device prepared by transferring mechanically exfoliated PtSe 2 nanoribbon from bulk crystal onto a Si/SiO 2 (270 nm) substrate 35 .…”

“…As the thickness decreases down to bi‐ and mono‐layer limit, a ferromagnetic‐to‐antiferromagnetic crossover is observed in the semiconducting PtSe 2 (Figure 6D–F). 36 DFT calculations suggest that surface Pt vacancies ( V Pt ) trigger the thickness‐dependent magnetic ordering. In the PtSe 2 ML, a magnetic moment of 4.0 μ B induced by a Pt vacancy is localized on the six surrounding Se atoms.…”

“…(E–F) Magnetic field dependence of graphene resistance with (E) monolayer and (F) bilayer PtSe 2 measured at T = 1.6 K. (G–H) Spin‐density distribution of the V Pt defect in (G) monolayer and (H) bilayer PtSe 2 . Reproduced with permission: 2020, Springer Nature Limited 36 . (I) The schematics illustrates the oscillating RKKY (Ruderman–Kittel–Kasuya–Yosida) interaction varying with the thickness of PtSe 2 slab, and the corresponding magnetic ground‐states.…”

Atomic Study on Defects in 2D PtSe2 Monolayers Using Electron Microscopy

“…Understanding different defect structures in 1T-PtX2 and their behaviours is vital for taking full advantage of them in tailoring materials properties. Theoretical studies have predicted the structures and stability of point defects in 1T-phase PtX2, as well as the affected electronic and magnetic properties, 4,[13][14][15] while the experimental research addressing the defects in monolayer PtX2 is still very limited so far, which is crucial for exploiting the great potential of PtX2 for extensive device applications. In this work, atomically thin PtSe2 films were grown using direct selenization method of ultrathin Pt layer at the atmospheric pressure in a chemical vapour deposition furnace.…”