Significant tuning of band structures of magneto-mechanical phononic crystals using extraordinarily small magnetic fields

Tuning band structures of a magneto-mechanical phononic crystal (PnC) (containing elastic plates bonded with magnets) is demonstrated by applying a small static magnetic field (Hdc). Due to magnetic torque effect, the markedly altered coupling between Bragg scattering (related to lattice constants) and local resonances of plates occurs. Consequently, significant tuning of band structures is observed under a greatly small Hdc. Experiments show that an additional passband occurs in band structures when Hdc ≥ 130 Oe. This threshold (130 Oe) is ∼1/100 as large as that of the conventional PnC using magnetostrictive materials. The adjusted maximum of passband bandwidth is 0.57 kHz under 0–600 Oe.