Writing and Detecting Topological Charges in Exfoliated Fe5-xGeTe2

Alex Moon, Yue Li, Conor McKeever, Brian W. Casas, Moises Bravo, Wenkai Zheng, Juan Macy, Amanda K. Petford-Long, Gregory T. McCandless, Julia Y. Chan, Charudatta Phatak, Elton J.G. Santos*, Luis Balicas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Fe5-xGeTe2 is a promising two-dimensional (2D) van der Waals (vdW) magnet for practical applications, given its magnetic properties. These include Curie temperatures above room temperature, and topological spin textures─TST (both merons and skyrmions), responsible for a pronounced anomalous Hall effect (AHE) and its topological counterpart (THE), which can be harvested for spintronics. Here, we show that both the AHE and THE can be amplified considerably by just adjusting the thickness of exfoliated Fe5-xGeTe2, with THE becoming observable even in zero magnetic field due to a field-induced unbalance in topological charges. Using a complementary suite of techniques, including electronic transport, Lorentz transmission electron microscopy, and micromagnetic simulations, we reveal the emergence of substantial coercive fields upon exfoliation, which are absent in the bulk, implying thickness-dependent magnetic interactions that affect the TST. We detected a “magic” thickness t ≈ 30 nm where the formation of TST is maximized, inducing large magnitudes for the topological charge density (∼6.45 × 1020 cm-2), and the concomitant anomalous (ρxyA,max ≃22.6 μΩ cm) and topological (ρxyu,T 1≃5 μΩ cm) Hall resistivities at T ≈ 120 K. These values for ρxyA,max and ρxyu,T are higher than those found in magnetic topological insulators and, so far, the largest reported for 2D magnets. The hitherto unobserved THE under zero magnetic field could provide a platform for the writing and electrical detection of TST aiming at energy-efficient devices based on vdW ferromagnets.

Original languageEnglish (US)
Pages (from-to)4216-4228
Number of pages13
JournalACS nano
Volume18
Issue number5
DOIs
StatePublished - Feb 6 2024

Funding

L.B. acknowledges support from the US DoE, BES program through award DE-SC0002613 US (synthesis and measurements), US-NSF-DMR 2219003 (heterostructure fabrication), and the Office Naval Research DURIP Grant 11997003 (stacking under inert conditions). J.Y.C. acknowledges NSF DMR-2209804 and the Welch Foundation through AA-2056-20220101. The National High Magnetic Field Laboratory acknowledges support from the US-NSF Cooperative agreement grant numbers DMR-1644779 and DMR-2128556 and the state of Florida. E.J.G.S. acknowledges computational resources through CIRRUS Tier-2 HPC Service (ec131 Cirrus Project) at EPCC ( http://www.cirrus.ac.uk ) funded by the University of Edinburgh and EPSRC (EP/P020267/1), ARCHER UK National Supercomputing Service ( http://www.archer.ac.uk ) via Project d429. E.J.G.S. acknowledges the EPSRC Open Fellowship (EP/T021578/1) and the Edinburgh-Rice Strategic Collaboration Awards for funding support. Work at Argonne (Y.L., C.P.) was funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Keywords

  • anomalous Hall effect
  • merons
  • skyrmions
  • topological Hall effect
  • topological charges

ASJC Scopus subject areas

  • General Engineering
  • General Materials Science
  • General Physics and Astronomy

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