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Large spin-orbit torque efficiency enhanced by magnetic structure of collinear antiferromagnet IrMn

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Science Advances  10 May 2019:
Vol. 5, no. 5, eaau6696
DOI: 10.1126/sciadv.aau6696
  • Fig. 1 Structure of L10-IrMn.

    (A) Schematic drawing of L10-IrMn unit cell. (B) XRD θ-2θ scan of IrMn along the (001) direction. Dotted lines show the reference peak positions of bulk L10-IrMn. a.u., arbitrary units. (C and D) RSMs around (113) and (103) planes, respectively. (E) HRTEM image of cross section of L10-IrMn thin film. Diffraction patterns from the substrate, interface, and IrMn are shown on the right.

  • Fig. 2 Neutron diffraction θ-2θ scans along different directions.

    (A) (001). (B) (110). (C) (100). (D) (−100). (E) (101). (F) (10-1).

  • Fig. 3 Measurement of SOT efficiency (θDL,m) from ST-FMR.

    (A) Schematics of measurement setup. The moment m in Py follows an elliptical precession route around the direction of H. It is influenced by two orthogonal torques τFL and τDL. Top right shows the optical image of the device and electrode (dark color). (B) Voltage spectra of L10-IrMn (22)/Py (17) measured from 8 to 12 GHz with nominal input power of 18 dBm. (C) Typical fitting of Vmix at 9 GHz. Vsym and Vasym correspond to the symmetric and antisymmetric components, respectively. (D) Fitting of Kittel equation. (E) θDL,m of L10-IrMn, p-IrMn, and Pt. The error bar describes 1 SD over at least five devices.

  • Fig. 4 Effect of Cu spacer and current direction on SOT efficiency (θDL,m) in L10-IrMn.

    (A) Vmix (data point) and its fit (line) of L10-IrMn (22)/Cu (0, 0.5, 1)/Py (13) at 9 GHz. The voltage spectrum is scaled for a clearer comparison. (C) Vmix (data point) and its fit (line) of devices on L10-IrMn (22)/Py (13) at 9 GHz. The angle refers to the orientation of the microstrip in the film plane relative to the [100] direction of the L10-IrMn lattice. The insets of (A) and (C) show the extracted θDL,m. (B and D) Linear fit of linewidths against frequency for devices in (A) and (C), respectively. Inset shows the extracted damping constant (α). The plot of the 0° device is too scattered and is therefore replaced by the 67.5° device in (D).

  • Fig. 5 In-plane angle dependence of SOT efficiency (θDL,m) and resonance condition (Hres).

    (A) Schematic illustration of device orientation. The blue rectangle illustrates that multiple devices are patterned from the same continuous film. (B, D, and F) Normalized θDL,m at 9 GHz of p-IrMn (22)/Py (13), L10-IrMn (22)/Py (13), and L10-IrMn (22)/Cu (0.5)/Py (13), respectively. (C, E, and G) Normalized resonant fields (Hres) at 9 GHz of devices in (B), (D), and (F) respectively. The angle refers to the orientation of the microstrip in the film plane relative to the [100] direction for L10-IrMn samples and an arbitrary axis for the p-IrMn sample.

  • Fig. 6 Schematics of orthogonal domains in collinear AFM.

    (A) Twined MnF2 (110) on MgO (001) according to (35). (B) L10-IrMn (001) on KTaO3 (001) based on analysis of the magnetic anisotropy in exchange-coupled Py. The axes refer to the crystal lattice of the respective AFM film.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaau6696/DC1

    Supplementary Materials and Methods

    Fig. S1. M-H loop of L10-IrMn/Py.

    Fig. S2. Typical ST-FMR results of L10-IrMn (22)/Py (13) from 5 GHz to 12 GHz.

    Fig. S3. Surface roughness of L10-IrMn film and its negligible effect on linewidth broadening.

    Fig. S4. Thickness dependence of SOT efficiency (θDL,m).

    Fig. S5. Dependence of damping constant (α) on Cu spacer and device orientation.

    Fig. S6. Dependence of SOT efficiency (θDL,m) and resonance condition (Hres) on device orientation.

    Fig. S7. Dependence of intrinsic SHC (normalized) on alignment of magnetic moment (m) in L10-IrMn and direction of electric current.

    Fig. S8. Electrical properties of L10-IrMn.

    Fig. S9. Harmonic Hall voltage measurement of the SOT in L10-IrMn.

    Table S1. Intrinsic SHC.

    References (4149)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • Fig. S1. M-H loop of L10-IrMn/Py.
    • Fig. S2. Typical ST-FMR results of L10-IrMn (22)/Py (13) from 5 GHz to 12 GHz.
    • Fig. S3. Surface roughness of L10-IrMn film and its negligible effect on linewidth broadening.
    • Fig. S4. Thickness dependence of SOT efficiency (θDL,m).
    • Fig. S5. Dependence of damping constant (α) on Cu spacer and device orientation.
    • Fig. S6. Dependence of SOT efficiency (θDL,m) and resonance condition (Hres) on device orientation.
    • Fig. S7. Dependence of intrinsic SHC (normalized) on alignment of magnetic moment (m) in L10-IrMn and direction of electric current.
    • Fig. S8. Electrical properties of L10-IrMn.
    • Fig. S9. Harmonic Hall voltage measurement of the SOT in L10-IrMn.
    • Table S1. Intrinsic SHC.
    • References (4149)

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