High Magnetic Sensitivity at the Coercive Field Induced by Shear Horizontal SAW in Polycrystalline FeGa Films

A Love wave device is designed to generate surface acoustic waves (SAWs) with strong shear-horizontal polarization, interacting with a polycrystalline Fe₇₂Ga₂₈ magnetostrictive layer. The shear strain induced by these waves at a frequency of ≈160 MHz, coupled with magnetoelastic effects, leads to domain magnetization oscillation, resulting in unique responses that are particularly pronounced near the coercive field. Experimental results reveal that the response of the sensor is highly sensitive to the angle between the applied magnetic field and the wave propagation direction, with profiles that can vary significantly depending on this angle, with some configurations resulting in practically opposite responses. A particularly relevant case arises when the magnetic field is aligned with the Love wave propagation direction. In this case, the sensor response shows mainly a monotonic increase with the magnetic field, except near the coercive field, where a sharp peak emerges and then abruptly collapses, resulting in a magnetic sensitivity of ≈5 Hz/nT (0.031 ppm nT⁻¹). This high sensitivity near the coercive field opens the door to the development of high-performance sensors, simplifying electronics while leveraging the key advantages of SAW technology, including low power consumption, compact size, real-time response, and portability. A theoretical model is also discussed to further understand the underlying phenomena and optimize the design of next-generation devices, which hold significant potential for sensor applications across various fields.