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 great ME coupling, and have received widespread attention in various application fields. The application of ME devices in wireless power transfer (WPT) is attractive due to their compactness and ability to operate at lower frequencies than conventional coils. However, traditional ME composites rely on permanent magnets or electromagnets to provide biased magnetic fields, thus leading to problems such as high noise, large size, and high cost, which significantly hinder the advancement of miniaturized and 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. Using the equivalent magnetization and nonlinear magnetostrictive constitutive relationship, a finite element simulation model for a self-biased ME transducer operating in L-T mode is constructed. The ME coupling performances without DC bias in bending vibration mode and stretching vibration mode are studied. Based on the model, the corresponding experimental samples are prepared for measurement. The measurement results are in agreement with the simulation data, thereby 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 under bending resonance mode. Its ME coefficient attains a notable value of 10.7 V·cm<sup>–1</sup>·Oe<sup>–1</sup> at 99.4 kHz, while ME power coefficient reaches 5.01 μW·Oe<sup>–2</sup> at 97.9 kHz. Its on-load ME power coefficient can reach up to 4.62 μW·Oe<sup>–2</sup> at 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> at 99.4 kHz and 82.13 μW·Oe<sup>–2</sup> at 99.0 kHz, respectively. The simulation results further show that the performance of the self-biased ME transducer can be significantly improved by increasing the thickness of the high permeability layer. For example, by increasing the Metglas layer thickness from 30 μm to 90 μm, both the ME coefficient and ME power coefficient increase rapidly by 2.47 times and 6.96 times the original values, respectively. Self-biased ME transducers effectively reduce the dependence on external bias magnetic field, thereby providing a good approach for applying and developing ME composites in low-frequency WPT systems.