Measurement of magnetic loss in ferromagnetic lamella using high sensitivity piezo-magnetic surface acoustic wave sensor

Magnetic field sensors combining surface acoustic waves (SAW) and magnetostrictive thin films have shown promising sensitivity in laboratory studies, but their translation into real-world applications has remained limited. In this work, we report the first practical deployment of a shear-horizontal SAW magnetic sensor for the characterization of ferromagnetic electrical steels, which are key materials for the fabrication of high-efficiency electrical machines. The proposed sensor design is built on a Quartz substrate and features a nanostructured TbCo₂/FeCo film (140 nm) overlaid with a 700 nm SiO₂ layer that enhances shear-wave confinement and protects the surface. The sensor chip is then integrated directly onto the surface of a ferromagnetic lamella. Using a compact radar-based RF circuit (AD8302 IC), we achieve phase-sensitive detection with a sensitivity of ~91 V/T and a noise spectral density of 83 nV/√Hz. Both static and dynamic magnetic losses were measured at the lamella surface, showing excellent agreement with Hall sensor benchmarks. This study establishes the first proof of concept for the application of SAW magnetostrictive sensors, demonstrating their potential as a powerful tool for the in-situ characterization and monitoring of ferromagnetic materials in electrical engineering.