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(a) SEM image of the Co/Py chessboard sample, with the Co dots appearing as darker squares, and the chosen unit cell shown as a blue square of side a = nm. (b) Brillouin p-p polarization spectrum for wavevector q = 0.8π/a along Γ-X. (c) Simulated top-view displacement profiles of observed modes. u, v, and w refer to longitudinal, shear horizontal, and shear vertical displacement components, respectively. (d) Brillouin p-p and p-s polarization spectra for q = 0.8π/a along Γ-M. (e) Simulated top-view displacement profiles of observed modes.
Experimental and calculated phononic dispersion relations of the Co/Py chessboard sample. Measured p-p and p-s polarization data are denoted by respective red and green dots, and calculated data by pink solid (shear-vertical-dominated modes) and green dashed (longitudinal-dominated modes) curves. Quasi-Rayleigh and quasi-Sezawa wave branches are denoted by RW and SW, respectively, while surface optical-like wave branch by Greek letters. Measured gaps are indicated by green regions.
(i) Calculated phononic band structures of the Co/Py chessboard sample. Shear-vertical-dominated and longitudinal-dominated modes are represented by pink solid and green dashed curves, respectively. (ii) Schematics of sample (Co – blue and Py – yellow) in real (top) and reciprocal (bottom) space. (iii) The w-displacements (shear vertical), color-coded according to the scale bar of Fig. 1, of selected modes for the M and X points.
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