Research ArticleAPPLIED SCIENCES AND ENGINEERING

Generation of charge current from magnetization oscillation via the inverse of voltage-controlled magnetic anisotropy effect

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Science Advances  05 Aug 2020:
Vol. 6, no. 32, eabc2618
DOI: 10.1126/sciadv.abc2618
  • Fig. 1 Schematic of the fabricated two-port device.

    The top and bottom contacts of the tunnel junction form port 1. Port 2 is a coplanar waveguide electrically insulated from the tunnel junction. The s-matrix of the device is measured as a function of magnetic field applied along polar angle θH and azimuthal angle ϕH. Vi, Vr, and Vt represent amplitudes of voltage waves incident from port 1, reflected into port 1, and transmitted to port 2, respectively. s11 and s21 parameters are defined as (Vr/Vi) and (Vt/Vi), respectively.

  • Fig. 2 Measurement of VCMA coefficient by FMR.

    (A) Absolute value of s22 parameter at 3 GHz as a function of external dc magnetic field applied along the x axis. The experimental data (magenta circles) are well modeled by the simulation (black curve). The inset shows resonance frequency as a function of a magnetic field. The red points are the experimental data, which are well modeled by the Kittel’s equation (blue line). (B) Absolute value of s22 parameter at 3 GHz as a function of external dc magnetic field applied along the x axis for three values of dc voltages applied across the tunnel junction. The shift of the resonance magnetic field is due to the VCMA effect. The inset shows variation of resonance magnetic field as a function of dc voltage.

  • Fig. 3 Real and imaginary parts of the transmission coefficients for magnetic field in z-x plane.

    (A) s12 and (B) s21 parameters after background subtraction and phase correction, as a function of external dc magnetic field applied at θH = 45° and ϕH = 0°. The red curve shows the real part, and black curve shows the imaginary part. Both s12 and s21 parameters are symmetric with respect to magnetic field.

  • Fig. 4 Angular dependence of s21 parameter.

    Normalized amplitude of s21 parameter versus θH. The experimental data are well modeled by sinθcosθ dependence, where θ denotes the polar angle of magnetization.

  • Fig. 5 Real and imaginary parts of the transmission coefficients for magnetic field in y-z plane.

    (A) s12 and (B) s21 parameters after background subtraction and phase correction, as a function of external dc magnetic field applied at θH = 45° and ϕH = 90°. The red curve shows the real part, and black curve shows the imaginary part. Both s12 and s21 parameters are antisymmetric with respect to magnetic field.

  • Fig. 6 Model for inverse VCMA effect.

    (A) The magnetization direction of the FM layer is oscillating. (B) The oscillating magnetization produces charge current due to the inverse VCMA effect, which can be modeled as a current source I with internal impedance of the FM/dielectric tunnel junction in parallel. I is given by μ0Ms(tFM/tMgO)λ area (dmz2/dt).

Supplementary Materials

  • Supplementary Materials

    Generation of charge current from magnetization oscillation via the inverse of voltage-controlled magnetic anisotropy effect

    Ambika Shanker Shukla, Akanksha Chouhan, Rachit Pandey, M. Raghupathi, Tatsuya Yamamoto, Hitoshi Kubota, Akio Fukushima, Shinji Yuasa, Takayuki Nozaki, Ashwin A. Tulapurkar

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