Self-Biased Magnetic Field Sensors Based on Surface Acoustic Waves through Angle-Dependent Magnetoacoustic Coupling

Surface-acoustic -wave-(SAW) based devices emerge as promising technology in magnetic field sensing by integrating a magnetostrictive layer with the giant AE/AG effect. However, almost all SAW magnetic field sensors require a bias field to obtain high sensitivity. In addition, the true nature of magnetoacous-tic coupling still presents a major challenge in understanding and designing this kind of device. Here, a dynamic magnetoelastic model for the AE/AG effect is established in consideration of the important role of the dipole-dipole interaction. The model is also implemented in finite-element-method software to cal-culate the resonance-frequency responses of multiple fabricated sensors with different * angles between the acoustic wave vector and the induced uniaxial magnetic anisotropy. The measured results are in excel-lent agreement with the simulated ones. A strong resonance-frequency sensitivity (SRF) of 630.4 kHz/Oe is achieved at zero bias field for the device with an optimized * angle. Furthermore, the SRF measurements along different directions verify its vector-sensing capability.