Dynamic Magnetoelastic Coupling-Driven Surface Acoustic Wave Based 2-D Vector Magnetic Field Sensor

Abstract

This study proposes a directivity model for surface acoustic wave (SAW) vector magnetic field sensing based on dynamic magnetoelastic coupling. The model, derived by combining magnetoelastic mechanics and the SAW propagation theory, was experimentally validated. The relationship between the ${\Delta } {E}/{\Delta } {G}$ effect of the magnetic film in a 2-D magnetic field and the sensing response was elucidated through the dynamic magnetoelastic coupling model. Additionally, the angular distribution of the magnetic field in space was quantitatively calibrated to construct a directivity model for SAW-based magnetic field sensing. A 200 nm aluminum electrode layer, 600 nm silicon dioxide waveguide layer, and 300 nm (Fe₉₀Co₁₀)₇₈Si₁₂B₁₀ magnetic film were deposited successively on an ST-90°X piezoelectric quartz substrate using photolithography and magnetron sputtering. The developed sensing device was integrated with a discriminative circuit to create a 200 MHz SAW vector magnetic field sensor. A test platform using a Helmholtz coil was constructed to evaluate the sensor performance. The sensor exhibited a maximum sensitivity of, lower detection limit of ${1.3905} \times {10}^{-{3}}$ Oe, response error of less than 0.139%FS, and directivity mode error of less than 2.16% FS. These results demonstrate that the developed sensor features excellent sensitivity, directivity, stability, and repeatability.