Self-biased vector magnetic sensor based on a Love-type surface acoustic wave resonator

Abstract

Magnetic sensors based on the interaction between the delta-E effect and surface acoustic waves (SAWs) are promising devices due to their simple driving circuits. In this study, a magnetic sensor composed of a (Fe90Co10)78Si12B10 magnetic layer and Love-type SAW resonator was investigated. The resonance frequency sensitivities (RFS) of the sensor resulting from the delta-E effect are 76.06 Hz/μT and 364.28 Hz/μT in the L-direction (along the easy axis) and W-direction (along the hard axis), respectively. The maximum RFS achieved by this magnetic sensor is 663.98 Hz/μT along the hard axis, with a resonance frequency of 221.76 MHz. The shift of resonance frequency shows a good linearity along with the external magnetic field in the L-direction. The curves of frequency response demonstrate point symmetry rather than the expected axial symmetry in both directions, due to the existence of residual magnetization. Non-zero RFS at zero magnetic field also appears in this device, because of the non-zero change of the Young's modulus at zero magnetic field. The good linearity and high sensitivity mean that the investigated magnetic sensor can be applied for weak DC magnetic field detection.