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Propriétés structurales et magnétiques de composés intermétalliques à base des terres rares, cobalt et silicium

Abstract : The Si for Co substitution in the RCo5 intermetallic compounds induces important modifications of the magnetic and crystal properties of this series of compounds.
The solubility limit of Si in RCo5 is temperature dependent. All the compounds have a CaCu5 type structure, but no Co-Co dumbbells are needed for the stabilization of this structure. The Si atoms are localized exclusively at the 3g crystallographic sites in all the compounds, regardless of the substitution percentage or of the R atom nature. This site has the particularity of having the maximum R atoms in the first vicinity. The c lattice parameter decreases upon Si/Co substitution.
In some of the heavy rare earth compounds (TbCo5-xSix, HoCo5-xSix) crystal symmetry change was observed. The symmetry lowers from hexagonal to orthorhombic with the reduction of the temperature. The symmetry change is due to the small displacement, along [210]hexa crystallographic direction, of the Co2c atoms to positions closer to the R atoms. This phenomenon is related to the particular alignment of the magnetic moments in the (a, b) plane.
The Si/Co substitution has an important influence both on the itinerant magnetism of Co and on the localized one of R. The Tc and µCo decrease fast upon Si substitution. These modifications are due to the reduction of the exchange field and to the 3d(Co)-3p(Si) hybridization. Combining different magnetisation measurement with neutron diffraction the magnetic phase diagrams were elaborated for the RCo5-xSix systems.
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https://tel.archives-ouvertes.fr/tel-00290108
Contributor : Natalia Coroian <>
Submitted on : Tuesday, June 24, 2008 - 4:32:52 PM
Last modification on : Thursday, November 19, 2020 - 1:00:55 PM
Long-term archiving on: : Friday, May 28, 2010 - 8:51:35 PM

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  • HAL Id : tel-00290108, version 1

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Natalia Coroian. Propriétés structurales et magnétiques de composés intermétalliques à base des terres rares, cobalt et silicium. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2008. Français. ⟨tel-00290108⟩

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