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Titanium dx y ferromagnetism at the LaAlO3/SrTiO3 interface

Nature Materials volume 12, pages 703–706 (2013)Cite this article

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Abstract

A number of recent transport and magnetization studies have shown signs of ferromagnetism in the LaAlO3/SrTiO3 heterostructure1,2,3,4,5,6, an unexpected property with no bulk analogue in the constituent materials. However, no experiment thus far has provided direct information on the host of the magnetism7,8,9,10,11. Here we report spectroscopic investigations of the magnetism using element-specific techniques, including X-ray magnetic circular dichroism and X-ray absorption spectroscopy, along with corresponding model calculations. We find direct evidence for in-plane ferromagnetic order at the interface, with Ti3+ character in the dx y orbital of the anisotropic t2g band. These findings establish a striking example of emergent phenomena at oxide interfaces.

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Figure 1: X-ray magnetic circular dichroism (XMCD) on a LaAlO3/SrTiO3 heterostructure.
Figure 2: Characterizing the Ti valence state along the depth profile.
Figure 3: Spectroscopic diagram of the LAO/STO interface.
Figure 4: Hybridization effects of Ti with neighbouring oxygen.

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Acknowledgements

We thank D. Nordlund, H. Ohldag and D. Brehmer for experimental assistance in the spectroscopic measurements, and C. Chen, T. Devereaux, B. Kalisky and K. Moler for useful discussions. Synchrotron studies were carried out at the SSRL, a Directorate of SLAC and an Office of Science User Facility operated for the US DOE Office of Science by Stanford University. Y.W.X. acknowledges partial funding from the US Air Force Office of Scientific Research (FAQSSO-10-1-0524). J.L., H.K.S., C.B., Y.H., and H.Y.H. acknowledge support by the Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under contract DE-AC02-76SF00515.

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Authors and Affiliations

  1. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

    J.-S. Lee & C.-C. Kao

  2. Department of Applied Physics, Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA

    Y. W. Xie & H. Y. Hwang

  3. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

    H. K. Sato, C. Bell, Y. Hikita & H. Y. Hwang

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  1. J.-S. Lee
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  6. H. Y. Hwang
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Contributions

J.L., H.Y.H. and C.K. designed this project. J.L. and C.K. carried out the spectroscopy experiments. J.L., H.Y.H. and C.K. analysed the data and wrote the manuscript. Y.W.X., H.K.S., C.B., Y.H. and H.Y.H. grew and characterized the samples.

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Correspondence to J.-S. Lee.

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Lee, JS., Xie, Y., Sato, H. et al. Titanium dx y ferromagnetism at the LaAlO3/SrTiO3 interface. Nature Mater 12, 703–706 (2013). https://doi.org/10.1038/nmat3674

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