Proximity induced ferromagnetism at the interface between a topological insulator (TI) Bi$_{2}$Se$_{3}$ and a ferromagnetic insulator (FI)

ORAL

Abstract

The ferromagnetic phase of the surface states of a TI is predicted to carry many exotic properties, for example quantum anomalous Hall effect, magnetic monopole, and magneto-electric effects etc. In our study, we explore this novel phase utilizing the proximity induced exchange splitting to introduce ferromagnetism close to the surface of the Bi$_{2}$Se$_{3}$ film. High quality Bi$_{2}$Se$_{3}$ thin films were grown using molecular-beam-epitaxy, and in-situ deposited the ferromagnetic insulator (FI) EuS over this film. Magnetization measurements demonstrated a magnetic moment of more than 7$\mu _{B}$ per Eu$^{2+}$ ion (bulk value), and reaching up to 11$\mu _{B}$ per Eu$^{2+}$ ion for 1nm thick EuS film, showing the unambiguous existence of excess ferromagnetism. The transport studies of these TI/FI bilayers unveiled a clear switching behavior of the magnetoresistance in the Bi$_{2}$Se$_{3}$ film. There was significant temperature dependence seen in both MR and the coercivity. Due to the near range nature of the exchange interactions, these extra magnetic moments and the MR results are attributed to come from the induced ferromagnetism at the Bi$_{2}$Se$_{3}$ surface.

*Work supported by ONR grant N00014-09-1-0177, NSF grant DMR 0504158 and NSF DMR 08-19762 (CMSE - Initiative 2)

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Authors

  • Peng Wei

    • MIT, Francis Bitter Magnet Lab
    • Francis Bitter Magnet Lab, MIT, Cambridge, MA
    • FBML, MIT, Cambridge, USA
    • FBML, MIT

  • F. Katmis

    • MIT, Francis Bitter Magnet Lab
    • Francis Bitter Magnet Lab, MIT, Cambridge, MA
    • MIT
    • Department of Physics, MIT, Cambridge, USA

  • Badih Assaf

    • Physics Dept. Northeastern University
    • Physics Department, Northeastern University, Boston, MA

  • Don Heiman

    • Northeastern University
    • Physics Department, Northeastern University
    • Physics Dept. Northeastern University
    • Physics Department, Northeastern University, Boston, MA

  • Pablo Jarillo-Herrero

    • MIT
    • Massachusetts Institute of Techology
    • Physics Department, MIT, Cambridge, MA
    • Department of Physics, MIT, Cambridge, USA
    • Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
    • Massachusetts Institute of Technology

  • Jagadeesh S. Moodera

    • Massachusetts Institute of Technology
    • MIT, Francis Bitter Magnet Lab
    • Francis Bitter Magnet Lab and Physics Department, MIT, Cambridge, MA
    • MIT
    • Department of Physics, MIT, Cambridge, USA
    • Francis Bitter Magnet Lab.
    • FBML and Physics Dept., MIT