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Coexistence of magnetic order and two-dimensional superconductivity at LaAlO3/SrTiO3 interfaces

Nature Physics volume 7, pages 762–766 (2011)Cite this article

Abstract

A two-dimensional electronic system forms at the interface between the band insulators1,2 LaAlO3 and SrTiO3. Samples fabricated until now have been found to be either magnetic or superconducting, depending on growth conditions3,4. Combining high-resolution magnetic torque magnetometry and transport measurements, we report here magnetization measurements providing direct evidence of magnetic ordering of the two-dimensional electron liquid at the interface. The magnetic ordering exists from well below the superconducting transition to up to 200 K, and is characterized by an in-plane magnetic moment. Surprisingly, despite the presence of this magnetic ordering, the interface superconducts below 120 mK. This is unusual because conventional superconductivity rarely exists in magnetically ordered metals5,6. Our results suggest that there is either phase separation or coexistence between magnetic and superconducting states. The coexistence scenario would point to an unconventional superconducting phase as the ground state.

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Figure 1: Torque magnetometry of LAO/STO oxide interface.
Figure 2: Coexistence of superconductivity and magnetic ordering in a 5 u.c. LAO/STO interface sample.
Figure 3: Magnetic ordering persisting to elevated temperature.
Figure 4: Angular dependence of the interface torque indicating an in-plane saturation magnetic moment.

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Acknowledgements

The authors acknowledge discussions with D. Grundler, T. Kopp, P. A. Lee and G. A. Sawatzky, and experimental assistance from T. Murphy, J-H. Park and S. Hannahs. This work was supported by the Army Research Office (54173PH), by the Deutsche Forschungsgemeinschaft (TRR 80) and by the EC (OxIDes). L.L. would like to thank the MIT Pappalardo Fellowships in Physics for their support. The high-field experiments were performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement DMR-084173, by the State of Florida and by the DOE.

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Authors and Affiliations

  1. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    Lu Li & R. C. Ashoori

  2. Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany

    C. Richter

  3. Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany

    J. Mannhart

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  1. Lu Li
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Contributions

The studies were designed, planned and analysed by all authors, who also wrote the manuscript. C.R. grew the samples; L.L. carried out the torque and resistivity measurements and the data analysis.

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Correspondence to R. C. Ashoori.

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Li, L., Richter, C., Mannhart, J. et al. Coexistence of magnetic order and two-dimensional superconductivity at LaAlO3/SrTiO3 interfaces. Nature Phys 7, 762–766 (2011). https://doi.org/10.1038/nphys2080

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