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The concept of the proposed magnonic architecture is presented. (a) Schematic illustration of a transducer act as spin wave source in a magnonic chip (depicted in (b)) is shown together with the geometry and notations corresponding to the analytical “toy model.” (c) The rotating stray magneto-dipole field induced by the magnetization precessing in the magnonic transducer is displayed, given that the magnonic chip is subjected to microwave signal shown in (d). (e) The coefficient of field enhancement on the top surface of waveguide is shown as a function of the spacing between the transducer and the waveguide. (f) The instantaneous spatial profiles of themagneto-dipole field resonantly produced by the x and z component of the dynamical magnetization of the transducer on the waveguide top surface for d = 0 are shown (blue solid and red dotted lines, respectively) for the instant when the dynamical magnetization is aligned along the x direction. The transducer is centered at x = 0.
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(a) A scanned micrograph of the transducer on top of the waveguide is shown. The micrograph covers a region of 60 × 30 µm2. (b) Typical TRSKM signals acquired from the waveguide (blue curve) and transducer (red curve) are shown as yielded by experiments with a pulsed excitation. (c) Fourier spectra calculated from the TRSKM signals in the waveguide and the transducer (×2) are shown by the blue and red curves, respectively. (d) Dispersion relation of Damon-Eshbach spin wave inside the waveguide (blue curve). The red straight lines indicate resonance frequency of the additional peak of the transducer and the predicted wave vector value of the emitted spin waves. (e)–(l) TRSKM images acquired at time delays of 0.0, 26.7, 46.7, 60.0, 80.0, 100.0, 120.0, and 133.3 ps, respectively, are shown.
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(a) Ground state of the waveguide plus transducer (static magnetization My ) under zero field. 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 10 nm spacing from the overlaid 50 nm wide, 150 nm long, and 30 nm thick transducer. Little arrows inside the waveguide and transducer represent local magnetic moment direction. (b)–(d) The spatial distributions of z component dynamic magnetization m z inside the waveguide are shown for relative simulation times of 0, 21.7, and 43.5 ps, respectively. Inset of (a): Color scale for My in (a) and m z in (b)–(e) with range of −40 to 40 Oe and −0.2 to 0.2 Oe, respectively. (e) Dynamic magnetization m z inside waveguide at 0 ps with transducer static magnetization point towards negative y direction. (f) The dispersion relation of spin waves inside the magnonic waveguide (blue) is shown together with the line (red) representing uniform FMR frequency of the transducer. (g) The spectral density of the excited spin waves is plotted as a function of wave vector k/2π in the waveguide. Inset of (g): Cross section of micrometer wide microstrip carrying a rf current running out of page resulted in rf Oersted field represented by elliptical lines. Red boxes and yellow thin slab represent the transducers and waveguide sitting underneath, respectively.
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We use time resolved scanning Kerr microscopy and analytical and numerical calculations to demonstrate coupling of uniform global microwave field to propagating spin waves for emerging magnonic architectures. The coupling is mediated by the local dynamic dipolar field produced by the magnetization of a resonantly driven all-metallic magnetic microwave-to-spin-wave transducer. The local dipolar field can exceed that of the incident microwave field by one order of magnitude. Our numerical simulations demonstrate the ability of the transducer to unidirectionally emit coherent exchange spin waves of nanoscale wavelengths with the emission direction programmed by the magnetic state of the transducer.
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