Low-magnetic-threshold acoustic switching utilizing magnetoelastic FeNi/brass phononic crystal plate

Summary form only given. Acoustic switches (ASs) can control the wave propagation in media for acoustic wave applications including smart acoustic structures and materials [1]. Especially, contactless magnetic-controlled AS based on magnetoelastic Terfenol-D/epoxy phononic crystals has been developed by exploiting external static magnetic fields [2]. However, the magnetic-controlled AS exhibits an ultra-high threshold of the magnetic field due to the small change in the wave coupling between phononic crystal elements under the external stimuli. In this paper, a low-magnetic-threshold AS using a magnetoelastic FeNi/brass phononic crystal plate is presented . This AS contains an elastic brass plate bonded with four magnetostrictive FeNi plates (two piezoelectric PZT plates are used as the elastic wave source and receiver, respectively) . Due to the magnetic field dependence of the magnetostriction, changes in elastic and geometrical characteristics of FeNi plates occur under static magnetic field (H_dc) . Because the small differences of elastic characteristics between brass and FeNi plates lead to the strong elastic wave coupling between them, these changes have great influences on bandgaps and wave transmission. Consequently, a smaller H_dc threshold for turning on/off is observed in the presented AS using a magnetoelastic FeNi/brass phononic crystal plate than in the previous AS based on a magnetoelastic Terfenol-D/epoxy phononic crystal. The experimental results show that acoustic switching can be achieved under the control of the magnetic field H_dc due to the sharp transition (1 .55%/Oe) of transmission between 67 Oe and 102 Oe. This proposed low-magnetic-threshold AS consisting of a magnetoelastic FeNi/brass phononic crystal plate exhibits an approximately 102 Oe threshold of the magnetic field and an 89.9% contrast rate at 249.3 kHz. This threshold (102 Oe) is approximately 1/118 as large as that of the previous AS based on a mag- etoelastic Terfenol-D/epoxy phononic crystal [2].