Shear Horizontal Mode Enhanced Magnetic Field Sensitivity in Strongly Coupled Magnetoacoustic Wave Sensor

ABSTRACT Surface acoustic wave (SAW) magnetic field sensors benefit from small size and low cost, but they are restricted from practical applications by poor sensitivity and limit of detection (LoD). Strong coupling, a stronger form of ferromagnetic resonance, has the potential to overcome these obstacles. While Rayleigh‐SAW exhibits limited magnon‐phonon coupling, shear horizontal (SH) SAW, with more energy concentrated near the surface, is promising to improve the sensing performance. Here, shear horizontal mode‐enhanced magnetic field sensitivity in a strongly coupled magnetoacoustic wave sensor is reported. Fittings of the dispersion anticrossing at different magnetic field directions confirm the achievement of strong coupling and tunability of the coupling regime. The sensor based on the SH mode achieves high frequency sensitivity of 2.13 MHz/Oe and phase sensitivity of 508.71 °/Oe and low LoD of 47 pT/Hz 1/2 @ 10 Hz, all of which are enhanced by an order of magnitude compared to the reported Rayleigh mode sensor. As a proof‐of‐concept, the mapping process in geophysical exploration is simulated, and the practical weak‐magnetic‐field detection capability of the miniaturized sensor is demonstrated. This work provides a new strategy to enhance the magnetic field sensitivity of the SAW sensor and opens up opportunities for practical weak magnetic sensing application scenarios.