Miniaturized ΔE-Effect Magnetic Field Sensors

Magnetic field sensors based on the ΔE-effect have emerged as promising candidates for detecting weak, low-frequency magnetic fields in biomedical applications. The ΔE-effect arises from the magnetic-field-dependent variation in the elastic modulus of magnetostrictive materials. When such a material is mechanically coupled to a piezoelectric layer and driven at resonance, external magnetic fields modulate the stiffness tensor, leading to measurable shifts in the sensor’s resonance frequency. Despite their advantages, cantilever-type macroscopic ΔE-effect sensors face limitations, including poor scalability, limited integration with microelectronics, and low reproducibility. This thesis presents a comprehensive investigation into the design, fabrication, characterization, and optimization of miniaturized ΔE-effect sensors. A double-wing microresonator design is introduced to suppress anchor-induced magnetic inhomogeneities, and a shadow-mask-based post-release deposition technique is implemented to mitigate residual stress typically introduced during fabrication. This approach significantly improves reproducibility. The frequency response and sensitivities are studied across multiple resonance modes. The performance of the sensors is explored through a detailed signal and noise analysis under varying measurement conditions. To generalize the findings from individual sensor analyses, a statistical study across a wide range of sensor geometries is conducted. Finally, strategies to further enhance sensor performance are explored, including multilayer magnetic films, exchange-biased and hard-biased configurations, magnetic flux concentrators, and sensor arrays. These concepts provide pathways to achieving bias-free operation, reduced magnetic noise, and enhanced sensitivity, paving the way for next-generation miniaturized ΔE-effect magnetic field sensors tailored to specific biomedical applications.

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