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.

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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.

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