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Ferromagnetic exchange, spin–orbit coupling and spiral magnetism at the LaAlO3/SrTiO3 interface

Nature Physics volume 9, pages 626–630 (2013)Cite this article

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Abstract

The electronic properties of the polar interface between insulating oxides is a subject of great interest1,2,3. An exciting development is the observation of robust magnetism4,5,6,7,8 at the interface of two non-magnetic materials, LaAlO3 (LAO) and SrTiO3 (STO). Here we present a microscopic theory for the formation and interaction of local moments that depends on essential features of the LAO/STO interface. We show that correlation-induced moments arise owing to interfacial splitting of orbital degeneracy. We find that conduction electrons with a gate-tunable Rashba spin–orbit coupling mediate ferromagnetic exchange with a twist. We predict that the zero-field ground state is a long-wavelength spiral. Its evolution in an external field accounts semi-quantitatively for torque magnetometry data5 and describes qualitative aspects of the scanning superconducting quantum interference device measurements6. We make several testable predictions for future experiments.

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Figure 1: Electronic orbitals and charge localization.
Figure 2: Spiral ground state and its evolution with field.
Figure 3: Torque magnetometry.

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Acknowledgements

We acknowledge stimulating conversations with L. Li, L. Balents, W. Cole, J. Mannhart, K. Moler, W. Pickett, S. Satpathy and N. Trivedi, and the support of DOE-BES DE-SC0005035 (S.B.), NSF-DMR-1006532 (O.E.) and NSF MRSEC DMR-0820414 (M.R.).

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Authors and Affiliations

  1. Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA

    Sumilan Banerjee, Onur Erten & Mohit Randeria

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  1. Sumilan Banerjee
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  2. Onur Erten
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  3. Mohit Randeria
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S.B., O.E. and M.R. contributed to the theoretical research described in the paper and the writing of the manuscript.

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Correspondence to Mohit Randeria.

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Banerjee, S., Erten, O. & Randeria, M. Ferromagnetic exchange, spin–orbit coupling and spiral magnetism at the LaAlO3/SrTiO3 interface. Nature Phys 9, 626–630 (2013). https://doi.org/10.1038/nphys2702

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