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Controlling the magnetic anisotropy in Cr2Ge2Te6 by electrostatic gating

Abstract

Electrical control of magnetism in van der Waals ferromagnetic semiconductors is an important step in creating novel spintronic devices, capable of processing and storing information, with these materials. For practical devices, electrical control at or near room temperature is sought, but most layered ferromagnetic semiconductors exhibit Curie temperatures below 100 K. Here, we show that electrostatic gating of thin chromium germanium telluride (Cr2Ge2Te6) crystals can be used to modulate the magnetic phase transition and magnetic anisotropy of this layered ferromagnetic semiconductor and increase its Curie temperature. Using an electric double-layer transistor device, we observe ferromagnetism in the material at temperatures up to 200 K and find that its magnetic easy axis is in the in-plane direction, in contrast to the out-of-plane easy axis of undoped Cr2Ge2Te6. Our analysis suggests that heavy doping promotes a double-exchange mechanism that is mediated by free carriers, which dominates over the superexchange mechanism of the original insulating state.

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Fig. 1: Gate-dependent transport properties of a CGT electric double-layer transistor device.
Fig. 2: MR hysteresis.
Fig. 3: Angle dependence of MR.
Fig. 4: Carrier density dependence of ferromagnetism.

Data availability

The data that support the plots within this Article and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

G.E. acknowledges the Singapore National Research Foundation for funding the research under its medium-sized centre programme. G.E. also acknowledges support from the Ministry of Education (MOE), Singapore, under AcRF Tier 2 (MOE2017-T2-1-134). H.K. acknowledges support from the Engineering and Physical Sciences Research Council through project EP/T006749/1. I.V. thanks J. Pu for assistance with ion gel preparation. F.Y.P. thanks S. Lei for fruitful discussions.

Author information

Affiliations

Authors

Contributions

I.A.V. and G.E. conceived the idea of the experiments. I.A.V. synthesized the CGT crystals and performed the transport measurements. H.C. and J.Z. conducted the first-principles calculations with input from Y.P.F. Data analysis and interpretations were carried out by H.K., I.A.V., G.E. and all other co-authors. I.A.V., G.E. and H.K. wrote the manuscript with input from the other co-authors.

Corresponding authors

Correspondence to Ivan A. Verzhbitskiy, Hidekazu Kurebayashi or Goki Eda.

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The authors declare no competing interests.

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Extended data

Extended Data Fig. 1 Angle dependence of MR at different temperatures and magnetic fields.

MR curves of the device #2 at VG = 3.7 V and T = 120 K (left panels) and 150 K (right panels). a, out-of-plane (γ = 90°) MR hysteresis. Unprocessed data are shown in the insets; b-d, angle-dependent MR curves for different planes as shown in the middle panels.

Extended Data Fig. 2 Reproducibility of the MR curves.

Multiple consecutive field-sweeps for T = 90 K and VG = 3.9 V (device #1).

Extended Data Fig. 3 In-plane MR hysteresis.

MR curves at different temperatures and VG = 3.1 V (device #1).

Extended Data Fig. 4 Gate-dependent ferromagnetism in device #2.

2D colour maps of \(\Delta {\mathrm{MR}} = \left| {{\mathrm{MR}}^ \uparrow \left( H \right) - {\mathrm{MR}}^ \downarrow \left( H \right)} \right|\) as a function of temperature and out-of-plane magnetic field for the device #2 at (a) VG = 2.7 V, (b) 2.8 V and (c) 3.7 V.

Extended Data Fig. 5 DFT projected density of states (pDOS) of CGT.

PDOS of (a-c) pristine (undoped) bulk CGT for d-orbitals of Cr, p-orbitals of Te and p-orbitals of Ge; (d-e) pDOS of Cr and Te in doped CGT (1.5\(e^ -\) per unit cell).

Supplementary information

Supplementary Information

Supplementary Figs. 1–4, Notes 1–5 and references.

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Verzhbitskiy, I.A., Kurebayashi, H., Cheng, H. et al. Controlling the magnetic anisotropy in Cr2Ge2Te6 by electrostatic gating. Nat Electron 3, 460–465 (2020). https://doi.org/10.1038/s41928-020-0427-7

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