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Etude et réductiοn des dérives en température aux basses fréquences des magnétοmètres à haute sensibilité à base de Μagnetο-Ιmpédance Géante (ΜΙG) : réduction des fluctuations l'offset en température

Alexandre Esper 1
1 Equipe Electronique - Laboratoire GREYC - UMR6072
GREYC - Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen
Abstract : The Giant Magneto-Impedance (GMI) effect is manifested by a strong variation in the impedance of a ferromagnetic conductor when an alternating current flows through it and it is submitted simultaneously to a variable magnetic field. Over the last few years, numerous research activities have been devoted to improving the field sensitivity of these devices. The values reached today make it possible to produce a very high sensitive magnetometer. However, only a few studies have investigated the temperature effects on the GMI material and its long-term stability. My thesis presents a detailed study of the temperature sensitivity of GMI magnetometers, and we proposed some methods to remedy the fluctuations induced by the temperature variation. Based on a theoretical model, an analytic study of the offset fluctuations generated by the temperature variations was carried out. This model takes into account the physic mechanisms involved when a temperature variation occurs, supposed to be the magnetic permeability and the electrical resistivity. From this modeling, a compensation technique for the different modes of operation has been proposed. Subsequently, a magnetometer prototype based on off-diagonal GMI wire was implemented to verify the effectiveness of the proposed method. The latter injects a double current modulation in the GMI sensitive element. The experimental results were compared to the classical configuration (simple modulation) and to the expected values. They show, on the one hand, the efficiency of this technique and, on the other hand, the coherence of the obtained results. A significant reduction in the GMI offset drift depending on temperature has been achieved, especially at very very low frequencies (< 10- 3 Hz) with a drift of - 1.8 nT/K for a temperature variation of 24 K, and a drift of 130 pT/h over 12 hours of acquisition.
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Alexandre Esper. Etude et réductiοn des dérives en température aux basses fréquences des magnétοmètres à haute sensibilité à base de Μagnetο-Ιmpédance Géante (ΜΙG) : réduction des fluctuations l'offset en température. Micro et nanotechnologies/Microélectronique. Normandie Université, 2019. Français. ⟨NNT : 2019NORMC247⟩. ⟨tel-02555537⟩

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