Research ArticleCONDENSED MATTER PHYSICS

Voltage controlled on-demand magnonic nanochannels

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Science Advances  02 Oct 2020:
Vol. 6, no. 40, eaba5457
DOI: 10.1126/sciadv.aba5457
  • Fig. 1 Determination of magnetization easy axis and schematic of the sample along with the representative BLS spectra.

    (A) Schematic diagram of device structure and experimental setup for measuring AHE and (B) the corresponding measured AHE signal from the CoFeB/MgO heterostructure with CoFeB thickness (tCoFeB) of 1.6 nm. (C) Schematic illustration of the CoFeB/MgO sample with a blanket ITO layer as the top electrode. (D) Stokes side of BLS spectra taken at IP transferred wave vector, k = 2.05 × 106 rad m−1, for applied gate voltage, VG = +4, 0, and −4 V, respectively, in the presence of the bias magnetic field, μ0H = 200 mT. The thick solid lines are theoretical fits with Lorentzian function, and the arrows describe the positions of the peak frequencies for VG = +4, 0, and −4 V, respectively, while the dotted line clarifies the relative shift in the frequencies with respect to VG = 0.

  • Fig. 2 Characterization of the CoFeB/MgO heterostructure with blanket ITO top electrode.

    (A) Variation of SW frequency as a function of bias magnetic field (μ0H) obtained from the CoFeB/MgO heterostructure with a blanket ITO top electrode for three values of gate voltage, VG = +4, 0, and −4 V. Symbols represent experimental data, while solid lines denote fitted curves using Eq. 2. (B) Variation of change in the iPMA field (μ0Hp) as a function of VG, where the solid line represents the linear fit. (C) Frequency (f) versus wave vector (k) dispersion curves for VG = +4, 0, and −4 V. Symbols show the experimental data points, while solid lines describe the fits to the data points using Eq. 2. The error bars in experimental data are contained within the symbols.

  • Fig. 3 Schematic of 1D-EFCMNC and its SW dispersion under the influence of applied voltage.

    (A) Schematic of the BLS measurement geometry used for the CoFeB/MgO heterostructure with 1D patterned ITO electrodes on top showing the incident (θ denotes the angle of incidence) and scattered light beams, the direction of the SW wave vector (k), and applied magnetic field H, with both vectors lying in the sample plane. (B) Periodic nature of electric field (EG) applied at the CoFeB/MgO interface, giving rise to two periodic regions, where region 1: top electrodes are absent and region 2: underneath the top electrodes. Stokes side of the BLS spectra taken at k = 2.05 × 106 rad m−1 (C) and k = 7.1 × 106 rad m−1 (D), obtained for VG = −4 V applied at μ0H = 200 mT. The theoretical fits using Lorentzian functions are shown by thick solid lines, and the SW peaks (M1 and M2) are indicated by the arrows. (E) Magnonic band structure under the influence of VG = −4 V applied at μ0H = 200 mT. Symbols represent peak frequencies in the BLS spectra, while blue lines denote SW intensities as calculated by PWM (the corresponding color map is given at the right side). The dashed vertical line indicates the position of anticrossing, and the corresponding magnonic BG is shown by the shaded region. The error bars in experimental data are contained within the symbols.

  • Fig. 4 SW nanochanneling in 1D-EFCMNC in the presence of an applied voltage.

    Spatial profiles of the SW modes for k = 2.05 × 106 rad m−1 (A) and k = 7.1 × 106 rad m−1 (B) under the application of VG = −4 V at μ0H = 200 mT. The color map and the geometry of H are shown at the center of the figure. Here, region 1 denotes the area without the top electrode, while region 2 represents the area beneath the top electrode.

  • Fig. 5 Reconfigurability of 1D-EFCMNC.

    Variation of SW frequency as a function of bias magnetic field (μ0H) at k = 2.05 × 106 rad m−1 obtained from (A) the CoFeB/MgO heterostructure with 1D patterned ITO electrodes without gate voltage, i.e., VG = 0, and (B) the reference CoFeB/MgO sample without any top electrode. The solid lines represent the fits with Eq. 2. The error bars in experimental data are contained within the symbols.

Supplementary Materials

  • Supplementary Materials

    Voltage controlled on-demand magnonic nanochannels

    Samiran Choudhury, Avinash Kumar Chaurasiya, Amrit Kumar Mondal, Bivas Rana, Katsuya Miura, Hiromasa Takahashi, YoshiChika Otani, Anjan Barman

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