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Magneto-ionic control of interfacial magnetism

Abstract

In metal/oxide heterostructures, rich chemical1,2, electronic3,4,5, magnetic6,7,8,9 and mechanical10,11 properties can emerge from interfacial chemistry and structure. The possibility to dynamically control interface characteristics with an electric field paves the way towards voltage control of these properties in solid-state devices. Here, we show that electrical switching of the interfacial oxidation state allows for voltage control of magnetic properties to an extent never before achieved through conventional magneto-electric coupling mechanisms. We directly observe in situ voltage-driven O2 migration in a Co/metal-oxide bilayer, which we use to toggle the interfacial magnetic anisotropy energy by >0.75 erg cm2 at just 2 V. We exploit the thermally activated nature of ion migration to markedly increase the switching efficiency and to demonstrate reversible patterning of magnetic properties through local activation of ionic migration. These results suggest a path towards voltage-programmable materials based on solid-state switching of interface oxygen chemistry.

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Figure 1: Cross-sectional TEM and EELS analysis.
Figure 2: Device schematics and voltage control of magnetic anisotropy.
Figure 3: Voltage-induced propagation of oxidation front.
Figure 4: Fast anisotropy switching by engineering electrode and oxide.
Figure 5: Effects of voltage and laser illumination on magnetic anisotropy.
Figure 6: Laser-defined anisotropy patterns and DW conduits.

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Acknowledgements

This work was supported by the National Science Foundation under NSF-ECCS -1128439 and through the MRSEC Program under DMR-0819762, and by the Samsung Global MRAM Innovation program. Technical support from D. Bono, M. Tarkanian and E. Shaw is gratefully acknowledged. Work was performed using instruments in the MIT Nanostructures Laboratory, the Scanning Electron-Beam Lithography facility at the Research Laboratory of Electronics, and the Center for Materials Science and Engineering at MIT. In situ TEM and EELS characterization was conducted using the facilities of the Aalto University Nanomicroscopy Center (Aalto-NMC) in Finland.

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Contributions

U.B. and G.S.D.B. conceived and designed the experiments. H.L.T. proposed the extension of studies to higher temperatures. U.B. prepared the samples with help from A.J.T. and S.E. U.B. performed the MOKE experiments and analysed the data. P.A. and U.B. conducted the VSM and AFM measurements. S.v.D. and L.Y. performed and analysed the TEM and EELS measurements. U.B. wrote the manuscript with assistance from G.S.D.B. and input from S.v.D. and L.Y. All authors discussed the results.

Corresponding author

Correspondence to Geoffrey S. D. Beach.

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The authors declare no competing financial interests.

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Bauer, U., Yao, L., Tan, A. et al. Magneto-ionic control of interfacial magnetism. Nature Mater 14, 174–181 (2015). https://doi.org/10.1038/nmat4134

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