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Arborescences magnétiques de fer et de cobalt élaborées par électrodéposition

Abstract : Magnetic arborescences of iron and cobalt were grown by electrochemical deposition in a thin cell. Only two morphologies were obtained, one ‘dense' with many branches at low concentration and one ‘sparse' with few thick branches at high concentration. The effect of a magnetic field on the growth is studied. In vertical field, perpendicular to the cell, the morphology of the deposits is not spiraling like in the case of non magnetic metals. A change of the morphology is however observed, stronger at high concentration. In horizontal field, at high concentration, the deposit grows in the direction of the field. In the case of iron at low concentration, the morphology change from isotropic and circular in zero field to rectangular in finite field. This symmetry breaking is explained as resulting from a selection of the orientation of the branches, associated with a minimization of the dipolar energy of the growing branches. TEM observations show that at nanometric scale the branches are single crystalline dendrites, the growth being realized without or in horizontal magnetic field. However, the vertical field effects appear at that scale as a distortion of the cubic cell in the case of iron and a flip of the c axis of the hexagonal cell in the case of cobalt. Magnetic properties of the arborescences show different magnetic behaviors for the dense and sparse arborescences. Dense arborescences show a behavior akin to that of ‘fine grains' while the sparse arborescences are not too different from the bulk material. These behaviors can be interpreted as resulting from a large size distribution of the branches. Finally, a new technique consisting in the deposition of a thin gold layer on one of the glass plates of the cell was used. Iron arborescences were thus obtained. The growth is not anymore dendritic and the magnetic behavior is modified.
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https://tel.archives-ouvertes.fr/tel-00005942
Contributor : Bodea Simona <>
Submitted on : Wednesday, April 21, 2004 - 3:19:20 PM
Last modification on : Friday, December 18, 2020 - 1:22:02 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:28:39 PM

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  • HAL Id : tel-00005942, version 1

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Simona Bodea. Arborescences magnétiques de fer et de cobalt élaborées par électrodéposition. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2000. Français. ⟨tel-00005942⟩

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