Thickness effects on magnetoelectric coupling for Metglas/PZT/Metglas laminates

Abstract

Thickness effects on the ME coefficient αME and electromechanical resonance frequency of Metglas/PZT/Metglas tri-layered laminates are investigated. The thickness of the magnetic plate is changed by assembling different numbers of the Metglas thin sheets (30 μm for each layer) while the PZT plate is maintained at constant thickness (0.5 mm). At 1 kHz of the applied alternating magnetic field, only one peak presents in the ME coefficient (αME) versus static magnetic field (HS) curve. As the thickness ratio n increases, the peak value of μME first increases and reaches a maximum at approximately n = 0.519, and then decreases afterward. The peak position (Hoptim) moves steadily toward a higher value as n increases. It is suggested that the relaxation factor k of the magnetic phase is reduced as n increases, causing the decrease of the piezomagnetic coefficient d11,m and the increase of Hoptim. By employing the micromechanics model and considering the degradation of d11,m with n, an optimized thickness ratio of 0.5 is predicted, which is in agreement with the experimental observations. The resonance frequency of the laminate increases with n, which is consistent with the calculation using a straightforward mixture law.