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(a) Ground state of the micromagnetic structure considered. The entire box of view in (a) represents a 2200 × 600 nm region. The magnonic waveguide of 100 nm width and of 10 nm thickness is separated by 5 nm spacing from the overlaid 50 nm wide, 150 nm long, and 30 nm thick resonator. Little arrows inside the waveguide and transducer represent local magnetic moment direction. (b)–(d) Out of plane magnetization (mz) inside the waveguide (static background subtracted) at the same relative simulation time for a vertical spacing between the resonator and the waveguide kept at 5 nm and changed to 20 and 50 nm, respectively. These images were recorded after the system has attained dynamic steady state. Inset of (a): Color scale for My in (a) and m z in (b)–(d) with range of −40 to 40 Oe and −0.2 to 0.2 Oe, respectively. (e) Ground state of the same structure but with the resonator magnetization flipped to the opposite direction. (f) Waveguide mz for case of opposite magnetized resonator at the same aforementioned relative simulation time. Resonator-waveguide spacing equals 5 nm both in (e) and (f).
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(a) and (b): Phase diagram of relative magnitude of the spin wave transmitted underneath the resonator measured at 200 nm in negative x direction away from the central axis of the resonator for static magnetization of the resonator pointing towards positive and negative y direction respectively. Note that α is plotted in logarithmic scale. (c) and (d): Identical to (a) and (b) but with magnitude of the spin wave replaced by oscillation phase (in radian). (e) and (f): Phase diagram of the precession magnitude of the resonator (averaged over the resonator volume) for static magnetization of the resonator pointing towards positive and negative y direction, respectively.
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(a)–(d) Dipolar stray field of the resonator at relative simulation time equal 0, 0.125, 0.25, and 0.375 T (T = 1/11.5 ns), respectively. (e) Spatial Fourier transform along x direction of the stray field z component at different vertical distance from the lower surface of the resonator (vertical axis, z).
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We have used micromagnetic simulations to demonstrate a method for controlling the amplitude and phase of spin waves propagating inside a magnonic waveguide. The method employs a nanomagnet formed on top of a magnonic waveguide. The function of the proposed device is controlled by defining the static magnetization direction of the nanomagnet. The result is a valve or phase shifter for spin waves, acting as the carrier of information for computation or data processing within the emerging spin wave logic architectures of magnonics. The proposed concept offers such technically important benefits as energy efficiency, non-volatility, and miniaturization.
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