Research ArticleMATERIALS SCIENCE

Above 400-K robust perpendicular ferromagnetic phase in a topological insulator

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Science Advances  23 Jun 2017:
Vol. 3, no. 6, e1700307
DOI: 10.1126/sciadv.1700307
  • Fig. 1 Proximity-induced ferromagnetism and AHE at 400 K in TIG/TI heterostructure.

    (A) Schematic drawing of proximity coupling between TI and TIG. (B) Exchange gap at the charge neutral point of TI surface states induced by broken time-reversal symmetry. (C) HRTEM image of a TIG/TI (20 QL) bilayer structure. (D and E) Hall traces of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.20 and 0.30, respectively. The upper insets show the corresponding temperature dependence of Rxx. The lower insets show schematic drawings of the corresponding chemical potential position.

  • Fig. 2 Temperature dependence of AHE response up to 400 K.

    (A) Hall resistance of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.20 (p-type) between 300 and 400 K. (B) Temperature dependence of AHE loops in (A) after subtracting the linear ordinary Hall background. (C) Hall resistance of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.30 (n-type) between 300 and 400 K. (D) Temperature dependence of AHE loops in (C) after subtracting the linear ordinary Hall background.

  • Fig. 3 Representative Andreev reflection spectra for (Bi0.20Sb0.80)2Te3 (20 QL) on TIG and sapphire substrate.

    Fitting the normalized differential conductance to the modified BTK model yields P of 32% for TI on TIG and near-zero P for TI on sapphire. All measurements were taken at 1.5 K. The circles are raw data and solid curves are the best fits. The inset is a schematic drawing of PCAR experiments.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/6/e1700307/DC1

    fig. S1. Structural and magnetic properties.

    fig. S2. Representative low-temperature anomalous Hall resistance loops of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.20 from 2 to 250 K.

    fig. S3. Representative low-temperature anomalous Hall resistance loops of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.30 from 2 to 250 K.

    fig. S4. Magnetoresistance (MR) of heterostructure samples.

    fig. S5. Anomalous Hall resistance over the entire temperature range.

    fig. S6. Hall voltage responses to an in-plane magnetic field, Hx, along the current direction for x = 0.20 at different temperatures.

    fig. S7. Longitudinal resistance of TIG/TI (x = 0.20) sample as a function of the out-of-plane magnetic field strength at selected temperatures between 50 and 400 K.

    fig. S8. Andreev reflection spectra and extracted spin polarization with different Z-factors.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Structural and magnetic properties.
    • fig. S2. Representative low-temperature anomalous Hall resistance loops of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.20 from 2 to 250 K.
    • fig. S3. Representative low-temperature anomalous Hall resistance loops of TIG/(BixSb1−x)2Te3 (5 QL) for x = 0.30 from 2 to 250 K.
    • fig. S4. Magnetoresistance (MR) of heterostructure samples.
    • fig. S5. Anomalous Hall resistance over the entire temperature range.
    • fig. S6. Hall voltage responses to an in-plane magnetic field, Hx, along the current direction for x = 0.20 at different temperatures.
    • fig. S7. Longitudinal resistance of TIG/TI (x = 0.20) sample as a function of the out-of-plane magnetic field strength at selected temperatures between 50 and 400 K.
    • fig. S8. Andreev reflection spectra and extracted spin polarization with different Z-factors.

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