Theoretical investigation of magnetoelectric surface acoustic wave characteristics of ZnO/Metglas layered composite

Abstract

The surface acoustic wave properties of piezoelectric/magnetostrictive layered structures consisting of insulating ZnO and metallic Metglas with giant Δ E effect were studied based on a stable scattering matrix method. Only the first Rayleigh mode was found with phase velocity between 2200 m/s and 2650 m/s, and the maximum electro-mechanical coupling coefficient about 1%. It was found that the center frequency of ZnO/Metglas is highly sensitive on the change of magnetic field, up to 440 MHz/Oe. However, there is a cutoff Young's modulus of Metglas for different designs of SAW, below which the Rayleigh mode will disappear. For a magnetoelectric SAW design with the center frequency of 335 MHz and covering a full magnetic field range from -1.4 to +1.4 Oe, the frequency sensitivity is 212 MHz/Oe, equivalent to a magnetic field sensitivity of 5 × 10-12 Tesla. Unlike conventional magnetoelectric bulk laminates or film stacks, the detection of frequency shift instead of electrical charge allows not only shrinkage of device volume but also a broad frequency band detection of weak magnetic field.