Etude expérimentale de la multifissuration et de la décohésion de films minces et nanostructures magnétiques sur substrats flexibles : effet sur l'anisotropie magnétique

Abstract : Flexible and stretchable magnetic systems are of increasing interest for the development of electromagnetic devices conformable to non-planar surfaces. In this context, the objective of this thesis is to identify the relationships between irreversible mechanical phenomena (cracking and delamination) at large strains and magnetic properties of thin films of nanometric thicknesses (CoFeB and NiFe alloys) deposited on polymer substrate (Kapton®) by magnetron sputtering. In a first time, tensile tests coupled in situ with atomic force microscopy or electrical resistance measurements were used to study thin film multifissuration and subsequent localized debonding (buckles). These measurements made it possible to highlight areas of macroscopic strains for which each mechanism was predominant. In addition, the adhesion energy could be discussed and estimated from the monitoring of the buckles under applied strain. In a second step, ferromagnetic resonance measurements carried out ex situ made it possible to link the previously identified areas of strains to the evolutions of the magnetic anisotropy of thin films. In addition, a correlation between strain heterogeneities and Gilbert damping coefficient was found. Finally, the magnetomechanical properties of NiFe nanowires arrays have made it possible to highlight the advantage of nanopatterning for these deformable magnetic systems.
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Skander Merabtine. Etude expérimentale de la multifissuration et de la décohésion de films minces et nanostructures magnétiques sur substrats flexibles : effet sur l'anisotropie magnétique. Mécanique des matériaux [physics.class-ph]. Université Sorbonne Paris Cité, 2017. Français. ⟨NNT : 2017USPCD058⟩. ⟨tel-02290650⟩

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