Work

High-Sensitivity SAW Magnetic Field Sensor Based on a Co 40 Fe 40 B 20 Bilayer

Year: 2025

Type: article

Abstract: In this work, a single-port surface acoustic (SAW) resonator with a Co40Fe40B20/SiO2/(X+90°) ST quartz multilayer structure is investigated as a magnetic field sensor. The Love wave resonator design is aimed at achieving a high magnetic field sensitivity, together with a temperature compensation. Two versions of sensitive layers are studied: Co40Fe40B20(100nm) and Co40Fe40B20(100nm)/SiO2(3nm)/Co40Fe40B20(100nm). For the latter, the 3 nm thick SiO₂ layer is inserted between two 100 nm thick amorphous Co40Fe40B20layers, with the objective of controlling the magnetic properties of the magnetoelastic layer. A quartz crystal is selected as the piezoelectric substrate and a 375 nm thick SiO2layer is used as insulating medium. This thickness is chosen to achieve insensitivity to temperature variations of the Love wave velocity at 433 MHz ISM band, when no magnetic field is applied. Optimized structures are fabricated and characterized, demonstrating a good agreement between experimental results and the simulation. The structure exhibits high magnetic field sensitivity of -6900 ppm/mT (corresponding to 3Hz/nT) along the hard axis with the 200nm total thickness of Co40Fe40B20bi-layer. A substantial 26-fold increase in magnetic field sensitivity is achieved compared to that of the 100 nm thick Co40Fe40B20.

Source: IEEE Sensors Journal

DOI: 10.1109/jsen.2025.3634136