Interface-induced room-temperature multiferroicity in BaTiO3

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Abstract

Multiferroic materials possess two or more ferroic orders but have not been exploited in devices owing to the scarcity of room-temperature examples. Those that are ferromagnetic and ferroelectric have potential applications in multi-state data storage if the ferroic orders switch independently, or in electric-field controlled spintronics if the magnetoelectric coupling is strong. Future applications could also exploit toroidal moments and optical effects that arise from the simultaneous breaking of time-reversal and space-inversion symmetries. Here, we use soft X-ray resonant magnetic scattering and piezoresponse force microscopy to reveal that, at the interface with Fe or Co, ultrathin films of the archetypal ferroelectric BaTiO3 simultaneously possess a magnetization and a polarization that are both spontaneous and hysteretic at room temperature. Ab initio calculations of realistic interface structures provide insight into the origin of the induced moments and bring support to this new approach for creating room-temperature multiferroics.

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Figure 1: Influence of ferroelectric polarization direction on TMR in Fe/BTO/LSMO and Co/BTO/LSMO junctions.
Figure 2: Element specific magnetic signals at Fe/BTO and Co/BTO interfaces.
Figure 3: Evidence for room-temperature multiferroicity.
Figure 4: Interface structure analysis.

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Acknowledgements

This study was partially supported by France-UK PHC Alliance program, the Triangle de la Physique contract ‘OXISPINTRONICS’, UK EPSRC EP/E026206/I, Region Île-de-France in the framework of C’Nano IdF, the European ESTEEM and the METSA networks and the European Research Council Advanced grant project ‘FEMMES’ (no. 267579). The ALICE diffractometer is funded through the BMBF Contract No. 05K10PC2. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 226716. X.M. acknowledges support from a Herschel–Smith fellowship. We also thank N. Reyren, V. Cros and F. Petroff for discussions.

Author information

S.V., V.G., A.B. and M.B. designed the experiments. X.M., N.D.M., R.O.C., C.D., K.B. and S.F. were responsible for the preparation and characterization of the samples. A.C., V.G., K.B., A.B. and M.B. performed the magnetotransport measurements and data analysis. S.V., A.C., V.G., A.Gaupp, L.B., R.A. and F.R. performed the XRMS, XAS and XMCD measurements and treated and interpreted the data. A.C., V.G., K.B. and S.F. carried out the PFM characterization. L.B. and A.Gloter performed the STEM-HAADF studies, the EELS measurements and interpreted the data. L.B., A.Gloter and A.Z. carried out the first-principles calculations and interpreted the results. S.V. and M.B. wrote the manuscript. All authors contributed to the manuscript and the interpretation of the data.

Correspondence to M. Bibes.

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