BEGIN:VCALENDAR VERSION:2.0 PRODID:-//linuxsoftware.nz//NONSGML Joyous v1.4//EN BEGIN:VEVENT SUMMARY:Magnetic sensors with superior performance: materials and design o ptimization for angular sensing DTSTART:20251003T160000Z DTEND:20251003T180000Z DTSTAMP:20260612T150024Z UID:a947cc08-d3ea-4c12-ba93-88d850bb49ad SEQUENCE:5 CREATED:20250929T085651Z DESCRIPTION:This thesis presents the optimization of magnetoresistive sens ors based on magnetic tunnel junctions (MTJs) for high-precision angular s ensing. The work combines numerical modeling\, material design\, and exper imental validation to develop sensors capable of achieving sub-degree angu lar accuracy with improved linearity and thermal stability. A macrospin St oner–Wohlfarth simulation framework was implemented to evaluate how magn etic anisotropies\, interlayer coupling\, and geometry influence sensor be havior. These simulations guided the design of optimized MTJ multilayers a nd led to the adoption of a Wheatstone bridge configuration with orthogona l reference layers to suppress non-linearities in the output signal.Protot ypes were fabricated using standard microfabrication techniques and charac terized under rotational magnetic fields and controlled temperature condit ions. The results show that the bridge-based configuration produces a near -sinusoidal output over 360° with angular deviation limited to ±2.5°\, representing a tenfold improvement over single-element sensors. The calcul ated angular error profile closely matches the experimental measurements\, confirming the validity of the model and indicating that residual error a rises from physical asymmetries in the device.Thermal stability was invest igated through annealing experiments and modeled using a grain-level therm al activation approach. The exchange-bias field was observed to degrade su bstantially at temperatures above 140°C\, in agreement with calculation r esults. These findings underscore the importance of material selection and stack engineering—such as buffer layer optimization and the use of high blocking-temperature antiferromagnets—for stable high-temperature opera tion.Overall\, the combination of simulation and experimental methods has enabled the development of a angular sensor with improved performance. The findings provide insight into the physical mechanisms that govern angle a ccuracy and establish a foundation for future sensors that combine high re solution with thermal robustness for demanding industrial and scientific a pplications.Link LAST-MODIFIED:20250930T095822Z LOCATION:Online URL:http://df.vps.tecnico.ulisboa.pt/pt/eventos/magnetic-sensors-with-supe rior-performance-materials-and-design-optimization-for-angular-sensing/ X-ALT-DESC;FMTTYPE=text/html:

This thesis present s the optimization of magnetoresistive sensors based on magnetic tunnel ju nctions (MTJs) for high-precision angular sensing. The work combines numer ical modeling\, material design\, and experimental validation to develop s ensors capable of achieving sub-degree angular accuracy with improved line arity and thermal stability. A macrospin Stoner–Wohlfarth simulation fra mework was implemented to evaluate how magnetic anisotropies\, interlayer coupling\, and geometry influence sensor behavior. These simulations guide d the design of optimized MTJ multilayers and led to the adoption of a Whe atstone bridge configuration with orthogonal reference layers to suppress non-linearities in the output signal.

Prototypes were fabricated using standard microfabr ication techniques and characterized under rotational magnetic fields and controlled temperature conditions. The results show that the bridge-based configuration produces a near-sinusoidal output over 360° with angular de viation limited to ±2.5°\, representing a tenfold improvement over singl e-element sensors. The calculated angular error profile closely matches th e experimental measurements\, confirming the validity of the model and ind icating that residual error arises from physical asymmetries in the device .

Thermal stabi lity was investigated through annealing experiments and modeled using a gr ain-level thermal activation approach. The exchange-bias field was observe d to degrade substantially at temperatures above 140°C\, in agreement wit h calculation results. These findings underscore the importance of materia l selection and stack engineering—such as buffer layer optimization and the use of high blocking-temperature antiferromagnets—for stable high-te mperature operation.

Overall\, the combination of simulation and experimental methods has enabled the development of a angular sensor with improved performance. The findings provide insight into the physical mechanisms that govern angle a ccuracy and establish a foundation for future sensors that combine high re solution with thermal robustness for demanding industrial and scientific a pplications.Link

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