Modeling and performance analysis of resonant self-biased magnetoelectric transducers

Abstract

Compared with single-phase multiferroic materials, magnetoelectric (ME) composites composed of piezoelectric and magnetostrictive materials have greater ME coupling, and have received widespread attention in various application fields. The employment of ME devices in wireless power transfer (WPT) applications is enticing, owing to their compactness and ability to operate at lower frequencies compared to conventional coils. However, conventional ME composites rely on permanent magnets or electromagnets to provide biased magnetic fields, resulting in problems such as loud noise, large size, and high cost, which significantly hinder the advancement of miniaturized, high-performance ME devices. To solve this problem, a self-biased ME laminated structure based on the magnetization grading effect is proposed in this work. Drawing upon the equivalent magnetization and nonlinear magnetostrictive constitutive rela-tionship, a finite element simulation model for a self-biased ME transducer operating in L-T mode has been constructed. The ME coupling performance without DC bias in both bending and stretching vibration modes is studied. Based on the model, the cor-responding experimental samples are prepared for measurement. The measured results agree with the simulation data, validating the accuracy and effectiveness of the model. The measured results show that the Metglas/Galfenol/PZT-5A structure can exhibit more significant self-biased ME effect under the stretching resonance mode than un-der bending resonance mode. Its ME coefficient attains a notable value of 10.7 V·cm<sup>-1</sup>·Oe<sup>-1</sup> @ 99.4 kHz, while ME power coefficient reaches 5.01 μW·Oe<sup>-2</sup> @ 97.9 kHz. Its on-load ME power coefficient can reach up to 4.62 μW·Oe<sup>-2</sup> @ 99.3 kHz without impedance matching. When an external bias magnetic field of 25 Oe is applied, these performance indexes increase significantly to 47.06 V·cm<sup>-1</sup>·Oe<sup>-1</sup> @ 99.4 kHz and 82.13 μW·Oe<sup>-2</sup> @ 99.0 kHz, respectively. The simulation results further show that the performance of the self-biased ME transducer can be significantly improved by in-creasing the thickness of the high permeability layer. For instance, by increasing the Metglas layer thickness from 30 μm to 90 μm, both the ME coefficient and ME power coefficient experience notable growths, surging to 2.47 times and 6.96 times their original values, respectively. Self-biased ME transducers effectively minimize reliance on external biased magnetic fields, thereby providing a good approach for the applica-tion and advancement of ME composites in low-frequency WPT systems.