Influence of the delta-E effect on a surface acoustic wave resonator

Abstract

Magnetic sensors based on the interaction between the delta-E effect and surface acoustic waves (SAWs) have been widely investigated. However, the influences of the delta-E effect on the SAW parameters have not been demonstrated systematically. Therefore, in this study, we performed a comprehensive analysis of the influences of the delta-E effect on the properties of a SAW resonator. The one-port SAW magnetic sensor had a four-layer structure composed of ST-cut 90° X quartz (piezoelectric substrate), Ta (interdigital electrode), SiO2 (insulating layer), and (Fe90Co10)78Si12B10 (magnetostrictive layer). The parameters of the SAW resonator such as the conductance spectrum, resonance frequency, full-width-at-half-maximum (FWHM) of the resonance frequency, Q-value, electromechanical coupling coefficient, and figure of merit were investigated. The change trends of the parameters followed the delta-E effect, except for the FWHM which exhibited an opposite trend. The magneto-elastic coupling efficiency of the magnetic layer varied with the change of external magnetic fields, which led to variation in the efficiency of electro-acoustic power conversion in the piezoelectric layer. We assume that this variation also contributed to the variation of the SAW parameters. These findings demonstrate that the variation of SAW resonator parameters is related not only to the delta-E effect but also to magneto-elastic coupling.