Investigation of Inverse Magnetostriction inCobalt Films and Nanowires

Abstract: In this thesis, a study of the inverse magnetostriction (the Villari effect) of Co nanowires and films is presented. The main objective was to investigate the stability of the Co nanowires’ magnetic properties, i.e., the coercivity and the saturation field under stress, in order to exploit them in flexible spintronic applications, for example, as spin injectors and detectors in spin transport circuits. To achieve our goal, we measured the hysteresis loops for the reference Co films samples and Co nanowires under various values of stress applied by curving the samples in specific molds by a homemade longitudinal magneto-optical Kerr effect (L-MOKE) setup at room temperature. In comparison with bulk Co, the Co film samples demoted their magnetostrictive behavior by one order of magnitude, due to a positive surficial magnetostrictive behavior at the interfaces. The Co nanowires reduced their magnetostrictive behavior further by about two orders of magnitude compared to the bulk Co, which means that they are magnetically stable to stress. This reduction in the magnetostrictive constant value may be related not only to the surface magnetostriction of the in-plane surfaces but also to the contribution of the out of plane surfaces. However, the extremely weak magnetostrictive response of the Co nanowires to stress is considered a promising feature that makes exploiting Co-nanowires in flexible spintronic devices interesting.