Report

Magnetization switching by magnon-mediated spin torque through an antiferromagnetic insulator

See allHide authors and affiliations

Science  29 Nov 2019:
Vol. 366, Issue 6469, pp. 1125-1128
DOI: 10.1126/science.aav8076
  • Fig. 1 Two types of spin-angular-momentum-transfer torque.

    (A) Illustration of the magnetization (M) reorientation driven by the electrical spin torque (ST) by means of the electrical spin current JS. (B) Illustration of the magnetization (M) reorientation driven by the magnon torque (MT) by means of the magnon current JM. AFM, antiferromagnet; FM, ferromagnet.

  • Fig. 2 Characterization of Bi2Se3/NiO/Py structures.

    (A) The exchange bias as a function of temperature for various NiO thicknesses (tNiO). (B) The blocking temperature deduced from (A). (C) The coercivity as a function of tNiO at room temperature. (D) X-ray diffraction patterns of sapphire substrate/Bi2Se3 (8 nm)/NiO (100 nm) and sapphire substrate/NiO (100 nm).

  • Fig. 3 ST-FMR measurement of magnon torque.

    (A) A diagram of the ST-FMR measurements, illustrating the magnetization precession driven by the spin torque, including the damping-like torque τDL and/or field-like torque τFL. The black arrow denotes the direction of IRF with a current density JC. The red and blue arrows indicate spin polarizations and magnon current JM, respectively. (B) A typical ST-FMR signal (open symbols) from a Bi2Se3/NiO (25 nm)/Py (6 nm) device at 10 GHz and 300 K with fits (solid lines), where the blue and green lines indicate the symmetric (VSFS) and antisymmetric Lorentzian (VAFA) component, respectively. (C) The spin torque ratio θi deduced from the ST-FMR data (solid circles) and the terahertz emission amplitude (open circles) as a function of tNiO at 300 K. The red curve is a fit using Eq. 1. For the fitting, we used ηθ = 0.8 and GA/F/σm=3×108 m–1. (Inset) The assumed magnon diffusion length (lm) as a function of tNiO. The star symbol corresponds to θi obtained from the ST-FMR measurement of the control device with 6-nm MgO insertion between Bi2Se3 and NiO layers. (D) Temperature dependence of θi for Bi2Se3/NiO (tNiO = 2, 5, and 25 nm)/Py (6 nm) devices.

  • Fig. 4 Magnetization switching induced by magnon torque in the Bi2Se3/NiO/Py devices at room temperature.

    (A) Illustration of the structure of the magnon torque switching device with an isolated Py rectangle defined on top of the NiO layer. (B) Optical microscope image of a device with electrodes, where the sample functional region is indicated with a red dotted box and an isolated Py rectangle is denoted with a yellow box. (C to F) MOKE images for magnon-torque-driven magnetization switching in the Bi2Se3/NiO (25 nm)/Py device by injecting a pulsed current I along the [(C) and (D)] +x axis or [(E) and (F)] –x axis at room temperature. (G to J) MOKE images for a Bi2Se3/NiO (5 nm)/Py device by injecting I along the [(G) and (H)] +x axis or [(I) and (J)] –x axis at room temperature. (K to N) MOKE images for the Bi2Se3/NiO (25 nm)/Cu (6 nm)/Py device by injecting I along the [(K) and (L)] +x axis or [(M) and (N)] –x axis at room temperature. In (C) to (N), the dark contrast represents the magnetization along the +y axis, and the light contrast represents the magnetization along the –y axis. The direction of magnetization is indicated with white arrows. The current density JC in the Bi2Se3 layer is denoted underneath each image.

Supplementary Materials

  • Magnetization switching by magnon-mediated spin torque through an antiferromagnetic insulator

    Yi Wang, Dapeng Zhu, Yumeng Yang, Kyusup Lee, Rahul Mishra, Gyungchoon Go, Se-Hyeok Oh, Dong-Hyun Kim, Kaiming Cai, Enlong Liu, Shawn D. Pollard, Shuyuan Shi, Jongmin Lee, Kie Leong Teo, Yihong Wu, Kyung-Jin Lee, Hyunsoo Yang

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

    Download Supplement
    • Materials and Methods 
    • Supplementary Text
    • Figs. S1 to S9
    • Table S1
    • References 

Stay Connected to Science

Navigate This Article