Magneto-acoustic sensing via ternary phononic crystal-engineered wave control

This study introduces a novel magnetic field sensor based on an acoustic wave device integrated with a phononic crystal (PnC) structure. Embedding PnCs within the acoustic platform enhances wave confinement and energy localization, significantly improving sensor sensitivity. The proposed PnC features a periodic ternary unit cell [Terfenol-DA/PMMA/Terfenol-DB]N, where magnetostrictive Terfenol-D layers of different thicknesses enable tunable mechanical properties under varying magnetic fields. This tunability modifies the phononic band gap width, providing a direct response to external magnetic field intensity. A modified transfer matrix method (TMM) is employed to analyze band gap behavior and reflectance variations. Simulation results show a clear correlation between magnetic field strength and band gap shifts. Optimized geometrical parameters yield high performance, with a sensitivity of 3880 Hz/Oe, Figure of Merit of 2.625 × 10⁻³ Oe⁻¹, detection limit of 537 × 10³ Oe, resolution of 2050.27 × 10⁶ Hz, and signal-to-noise ratio of 0.131, making it highly effective for magnetic sensing applications.