Defect induced, layer-modulated magnetism in ultrathin metallic PtSe2

Abstract

Defects are ubiquitous in solids, often introducing new properties that are absent in pristine materials. One of the opportunities offered by these crystal imperfections is an extrinsically induced long-range magnetic ordering,1 a long-time subject of theoretical investigations.1-3 Intrinsic, two-dimensional (2D) magnetic materials4-7 are attracting increasing attention for their unique properties including layer-dependent magnetism4 and electric field modulation6. Yet, inducing magnetism into otherwise non-magnetic 2D materials remains a challenge. Here, we investigate magneto-transport properties of ultrathin PtSe 2 crystals and demonstrate unexpected magnetism. Our electrical measurements show the existence of either ferromagnetic or antiferromagnetic ground state orderings depending on the number of layers in this ultra-thin material. The change in the device resistance upon application of a ~ 25 mT magnetic field is as high as 400 Ω with a magnetoresistance (MR) value of 5%. Our first-principles calculations suggest that surface magnetism induced by the presence of Pt vacancies and the Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange couplings across ultra-thin films of PtSe 2 are responsible for the observed layer-dependent magnetism. Considering the existence of such unavoidable growthrelated vacancies in 2D materials, 8,9 these findings can expand the range of 2D ferromagnets into materials that would otherwise be overlooked. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Two‐Dimensional Noble‐Metal Chalcogenides and Phosphochalcogenides

“…Whereas defect‐free PtSe 2 is diamagnetic, a transition to a half‐metallic ferromagnetic state for monolayer PtSe 2 at a critical strain of 5 % was predicted, which favors the formation of single Pt vacancies and may cause the p‐type conductance in PtSe 2. These point defects occur intrinsically in ultrathin 1 T ‐PtSe 2 layers, and Avsar et al . verified the emergence of magnetism as a result of vacancies in ultrathin metallic PtSe 2 both experimentally and theoretically.…”

“…Bulk 1 T ‐PdTe 2 is metallic and diamagnetic and was predicted to undergo a transition to a narrow‐gap semiconductor (about 0.14 eV) as a monolayer, whereas our calculations suggest a semimetallic state when SOC is included (Figures S11 and S12). Weak, temperature‐independent paramagnetism (μ≪μ B ) is usually observed, which might be caused by defects . PdTe 2 features rather strong interlayer interactions, but with a cleavage energy of 0.85 J m −2 , it should still be exfoliable (Table ).…”

Inducing Magnetic Phase Transitions in Monolayer CrI3 via Lattice Deformations

“…In these systems, the pivotal role played by the single-ion anisotropies preserves magnetic order in low dimensions [16], as unambiguously demonstrated by the groundbreaking exfoliation of the bulk ferromagnet CrI 3 down to the monolayer limit [17], rapidly followed by the appearance of many other ultrathin magnets, e.g. Fe 3 GeTe 2 , Cr 2 Ge 2 Te 6 , FePSe 3 [14,15,[18][19][20] Within the constantly expanding family of twodimensional magnets, semiconducting thin films of CrI 3 are arguably the most prototypical members. They exhibit a layered crystal structure, in which Cr atoms are located at the corners of in-plane honeycomb networks and reside in edge-sharing octahedra formed by I atoms [21].…”

Zweidimensionale Edelmetallchalkogenide und ‐phosphochalkogenide

“…Während defektfreies PtSe 2 diamagnetisch ist, wurde ein Übergang zu einem halbmetallischen ferromagnetischen Zustand bei Monolagen von PtSe 2 unter einer kritischen Streckung von 5 % vorhergesagt, was die Bildung von einzelnen Pt‐Fehlstellen fördert und der Grund für die p‐Typ‐Leitung in PtSe 2 sein könnte. Diese Punktdefekte tauchen intrinsisch in ultradünnen Schichten von 1 T ‐PtSe 2 auf, und Avsar et al . haben den daraus resultierenden Magnetismus experimentell und theoretisch bestätigt.…”