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Non-volatile electric control of spin–charge conversion in a SrTiO3 Rashba system

Abstract

After 50 years of development, the technology of today’s electronics is approaching its physical limits, with feature sizes smaller than 10 nanometres. It is also becoming clear that the ever-increasing power consumption of information and communication systems1 needs to be contained. These two factors require the introduction of non-traditional materials and state variables. As recently highlighted2, the remanence associated with collective switching in ferroic systems is an appealing way to reduce power consumption. A promising approach is spintronics, which relies on ferromagnets to provide non-volatility and to generate and detect spin currents3. However, magnetization reversal by spin transfer torques4 is a power-consuming process. This is driving research on multiferroics to achieve low-power electric-field control of magnetization5, but practical materials are scarce and magnetoelectric switching remains difficult to control. Here we demonstrate an alternative strategy to achieve low-power spin detection, in a non-magnetic system. We harness the electric-field-induced ferroelectric-like state of strontium titanate (SrTiO3)6,7,8,9 to manipulate the spin–orbit properties10 of a two-dimensional electron gas11, and efficiently convert spin currents into positive or negative charge currents, depending on the polarization direction. This non-volatile effect opens the way to the electric-field control of spin currents and to ultralow-power spintronics, in which non-volatility would be provided by ferroelectricity rather than by ferromagnetism.

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Fig. 1: Concept of ferroelectricity-controlled spin–charge conversion.
Fig. 2: Electric-field-controlled spin–charge conversion with electrical remanence.
Fig. 3: Electric polarization measurements.
Fig. 4: Field effect experiments.

Data availability

The data that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

The authors thank M. Cazayous, B. Dkhil, M. Maglione, S. Gambarelli and V. Maurel for useful discussions, as well as C. Carrétéro, E. Jacquet and Y. Gourdel for technical help. This work received support from the ERC Consolidator grant number 615759 “MINT”, the ERC Advanced grant number 833973 “FRESCO”, the QUANTERA project “QUANTOX”, the French Research Agency (ANR) as part of the “Investissement d’Avenir” programme (LABEX NanoSaclay, ref. ANR-10-LABX-0035) through project “AXION” and the Laboratoire d’Excellence LANEF (ANR-10-LABX-51-01) and ANR project OISO (ANR-17-CE24-0026-03). F.T. acknowledges support by research grant VKR023371 (SPINOX) from VILLUM FONDEN.

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Authors

Contributions

J.-P.A., P.N., L.V. and M.B. designed the experiment. J.-P.A., L.V. and M.B. supervised the study. D.C.V., L.M.V.A. and J.B. prepared the samples. P.N. performed the spin–charge conversion experiments with J.-P.A. and L.V. J.B., S.F. and M.B. performed the polarization measurements with the help of V.G. and F.T. F.T. and J.B. performed the transport experiments and analysed them with M.B. and A.B. M.B. and J.-P.A. wrote the paper with inputs from all authors.

Corresponding authors

Correspondence to Manuel Bibes or Jean-Philippe Attané.

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The authors declare no competing interests.

Additional information

Peer review information Nature thanks Dmitri E. Nikonov, Sashi Satpathy and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Gate-voltage dependence of the inverse Edelstein length in three different samples of NiFe(20 nm)/Al(0.9 nm)//STO.

The error bars are due to the small extra damping measured in this system. The estimated effective spin mixing conductance \({G}_{{\rm{eff}}}^{\uparrow \downarrow }\) is ranging from 1.2 nm−2 to 3.2 nm−2 with a mean value of 2.2 nm−2, leading to an injected spin current \({J}_{{\rm{S}}}^{{\rm{3D}}}\) ranging from 100 to 240 MA m−2 mT−2, with a mean value of 160 MA m−2 mT−2.

Extended Data Fig. 2 Spin-pumping signals obtained at 7 K on sample 2, for three different cool-downs from room temperature.

After each cool-down, the signal was measured before any gate-voltage application.

Extended Data Fig. 3 Spin-pumping and resistance loops of a NiFe/Al/STO sample.

Black data points, two-probe resistance R of a NiFe/Al/STO sample, measured in the spin-pumping setup as a function of the back-gate voltage. Red data points, normalized charge current production (Ic) measured by spin pumping.

Extended Data Fig. 4 Dependence of the produced current on the time spent after application of a positive or negative gate voltage.

Black squares, +200 V; red circles, −200 V. The measurements were performed at 7 K on sample 1.

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Noël, P., Trier, F., Vicente Arche, L.M. et al. Non-volatile electric control of spin–charge conversion in a SrTiO3 Rashba system. Nature 580, 483–486 (2020). https://doi.org/10.1038/s41586-020-2197-9

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