Omnidirectional magneto-acoustic coupling in acoustically driven magnetoelectric antenna with focused interdigital transducers

Abstract

Acoustically driven magnetoelectric (ME) antennas present a promising approach for achieving orders-of-magnitude miniaturization. However, conventional resonator-based ME antennas suffer from substantial acoustic energy leakage, which limits the effective utilization of the magneto-acoustic coupling effect in the magnetostrictive (MS) film. In this work, we propose and experimentally demonstrate a surface acoustic wave ME antenna based on a piezoelectric-on-insulator substrate. By employing focused interdigital transducers, we spatially confine acoustic waves, significantly enhancing the acoustic energy density within the MS film and thereby improving the efficiency of magneto-acoustic coupling. Experimental results reveal that with MS film loading, the antenna's radiated power increases by a factor of 32.55 compared to an unloaded reference structure, achieving a gain of −26.78 dBi, an electromechanical coupling coefficient (k2) of 8.79%, a quality factor (Q) of 217, and a figure of merit (FoM, k2×Qmax) of 19.07. Furthermore, applying an external bias magnetic field of 300 Oe modulates the magnetocrystalline anisotropy, leading to a 1.84% enhancement in the antenna's resonance characteristics and a 7.15% improvement in radiation performance. By varying the magnetic field orientations, we further verify the proposed structure's omnidirectional magneto-acoustic coupling behavior. These findings provide insights into the design of next-generation miniaturized antennas with enhanced performance and tunability.