Defects are ubiquitous in solids and often introduce new properties that are absent in pristine materials. One of the opportunities offered by these crystal imperfections is an extrinsically induced long-range magnetic ordering1, a long-time subject of theoretical investigations1,2,3. Intrinsic, two-dimensional (2D) magnetic materials4,5,6,7 are attracting increasing attention for their unique properties, which include layer-dependent magnetism4 and electric field modulation6. Yet, to induce magnetism into otherwise non-magnetic 2D materials remains a challenge. Here we investigate magneto-transport properties of ultrathin PtSe2 crystals and demonstrate an unexpected magnetism. Our electrical measurements show the existence of either ferromagnetic or antiferromagnetic ground-state orderings that depends on the number of layers in this ultrathin material. The change in the device resistance on the application of a ~25 mT magnetic field is as high as 400 Ω with a magnetoresistance 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 ultrathin films of PtSe2 are responsible for the observed layer-dependent magnetism. Given the existence of such unavoidable growth-related vacancies in 2D materials8,9, these findings can expand the range of 2D ferromagnets into materials that would otherwise be overlooked.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The data that support the findings of this study are available from the corresponding authors on reasonable request.
Esquinazi, P., Hergert, W., Spemann, D., Setzer, A. & Ernst, A. Defect-induced magnetism in solids. IEEE Trans. Magn. 49, 4668–4674 (2013).
Yazyev, O. V. & Helm, L. Defect-induced magnetism in graphene. Phys. Rev. B 75, 125408 (2007).
Osorio-Guillén, J., Lany, S., Barabash, S. V. & Zunger, A. Magnetism without magnetic ions: percolation, exchange, and formation energies of magnetism-promoting intrinsic defects in CaO. Phys. Rev. Lett. 96, 107203 (2006).
Huang, B. et al. Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit. Nature 546, 270–273 (2017).
Gong, C. et al. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals. Nature 546, 265–269 (2017).
Deng, Y. et al. Gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2. Nature 563, 94–99 (2018).
Bonilla, M. et al. Strong room-temperature ferromagnetism in VSe2 monolayers on van der Waals substrates. Nat. Nanotechnol. 13, 289–293 (2018).
Zhou, W. et al. Intrinsic structural defects in monolayer molybdenum disulfide. Nano Lett. 13, 2615–2622 (2013).
Zheng, H. et al. Intrinsic point defects in ultrathin 1T-PtSe2 layers. Preprint at https://arxiv.org/abs/1808.04719 (2018).
Hardy, W. J. et al. Very large magnetoresistance in Fe0.28TaS2 single crystals. Phys. Rev. B 91, 054426 (2015).
Wang, Z., Tang, C., Sachs, R., Barlas, Y. & Shi, J. Proximity-induced ferromagnetism in graphene revealed by the anomalous Hall effect. Phys. Rev. Lett. 114, 016603 (2015).
Guguchia, Z. et al. Magnetism in semiconducting molybdenum dichalcogenides. Sci. Adv. 4, eaat3672 (2018).
Gao, J. et al. Structure, stability, and kinetics of vacancy defects in monolayer PtSe2: a first-principles study. ACS Omega 2, 8640–8648 (2017).
Zhang, W. et al. Magnetism and magnetocrystalline anisotropy in single-layer PtSe2: interplay between strain and vacancy. J. Appl. Phys. 120, 013904 (2016).
Krasheninnikov, A. V. & Nordlund, K. Ion and electron irradiation-induced effects in nanostructured materials. J. Appl. Phys. 107, 071301 (2010).
Ciarrocchi, A., Avsar, A., Ovchinnikov, D. & Kis, A. Thickness-modulated metal-to-semiconductor transformation in a transition metal dichalcogenide. Nat. Commun. 9, 919 (2018).
Zhao, Y. et al. High-electron-mobility and air-stable 2D layered PtSe2 FETs. Adv. Mater. 29, 1604230 (2017).
Leven, B. & Dumpich, G. Resistance behavior and magnetization reversal analysis of individual Co nanowires. Phys. Rev. B 71, 064411 (2005).
Huang, F., Kief, M. T., Mankey, G. J. & Willis, R. F. Magnetism in the few-monolayers limit: a surface magneto-optic Kerr-effect study of the magnetic behavior of ultrathin films of Co, Ni, and Co–Ni alloys on Cu(100) and Cu(111). Phys. Rev. B 49, 3962–3971 (1994).
Song, T. et al. Giant tunneling magnetoresistance in spin-filter van der Waals heterostructures. Science 360, 1214–1218 (2018).
Klein, D. R. et al. Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling. Science 360, 1218–1222 (2018).
Ruderman, M. A. & Kittel, C. Indirect exchange coupling of nuclear magnetic moments by conduction electrons. Phys. Rev. 96, 99–102 (1954).
Kasuya, T. A theory of metallic ferro- and antiferromagnetism on Zener’s model. Prog. Theor. Phys. 16, 45–57 (1956).
Yosida, K. Magnetic properties of Cu–Mn alloys. Phys. Rev. 106, 893–898 (1957).
Zhang, K. et al. Experimental evidence for type-II Dirac semimetal in PtSe2. Phys. Rev. B 96, 125102 (2017).
Clark, O. J. et al. Dual quantum confinement and anisotropic spin splitting in the multivalley semimetal PtSe2. Phys. Rev. B 99, 045438 (2019).
Pizzochero, M. & Yazyev, O. V. Point defects in the 1T′ and 2H phases of single-layer MoS2: a comparative first-principles study. Phys. Rev. B 96, 245402 (2017).
Yu, X. et al. Atomically thin noble metal dichalcogenide: a broadband mid-infrared semiconductor. Nat. Commun. 9, 1545 (2018).
Žutić, I., Fabian, J. & Das Sarma, S. Spintronics: fundamentals and applications. Rev. Mod. Phys. 76, 323–410 (2004).
Han, W., Kawakami, R. K., Gmitra, M. & Fabian, J. Graphene spintronics. Nat. Nanotechnol. 9, 794–807 (2014).
Wen, H. et al. Experimental demonstration of XOR operation in graphene magnetologic gates at room temperature. Phys. Rev. Appl. 5, 044003 (2016).
Žutić, I., Matos-Abiague, A., Scharf, B., Dery, H. & Belashchenko, K. Proximitized materials. Mater. Today 22, 85–107 (2019).
Scharf, B., Xu, G., Matos-Abiague, A. & Žutić, I. Magnetic proximity effects in transition-metal dichalcogenides: converting excitons. Phys. Rev. Lett. 119, 127403 (2017).
Yang, T., Kimura, T. & Otani, Y. Giant spin-accumulation signal and pure spin–current-induced reversible magnetization switching. Nat. Phys. 4, 851–854 (2008).
Moodera, J. S., Kinder, L. R., Wong, T. M. & Meservey, R. Large magnetoresistance at room temperature in ferromagnetic thin film tunnel junctions. Phys. Rev. Lett. 74, 3273–3276 (1995).
Avsar, A. et al. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes. Nat. Phys. 13, 888–893 (2017).
Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).
Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).
Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).
Soler, J. M. et al. The SIESTA method for ab initio order-N materials simulation. J. Phys. Condens. Matter 14, 2745 (2002).
We acknowledge A. H. C. Neto for fruitful insights and discussions. We acknowledge the help of Z. Benes (CMI) with electron-beam lithography and K. Marinov for training on the measurement set-up. A.A., A.C., D.U. and A.K. acknowledge support by the European Research Council (ERC, grant 682332), Swiss National Science Foundation (grant 153298) and Marie Curie-Sklodowska COFUND (grant 665667). A.K. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no 785219 (Graphene Flagship). M.P. and O.V.Y. acknowledge support by the Swiss National Science Foundation (grants 162612 and 172543). First-principles simulations were carried out at the Swiss National Supercomputing Centre (CSCS) under project s832.
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Figs. 1–18.