Contribution à l'étude des propriétés structurales et magnétiques de siliciures et germaniures ternaires RTX, RTX2 et RT2X2 (R = La et lanthanoïdes ; T = Cr, Mn, Fe, Co)

Abstract : This thesis reports on the structural and magnetic properties of ternary RTX, RTX2 and RT2X2 (R = Lanthanides; T = Cr, Mn, Fe, Co ; X = Si, Ge) isotypic with CeFeSi or TiNiSi, LaMnSi2 and ThCr2Si2, respectively. The accurate determination of the atomic coordinates in the CeFeSi-type RTX compounds by X-ray single crystal analysis allows us to specify the crystal-chemistry of these materials. We thus shown that the structural transition "CeFeSi-TiNiSi" results from the interplay of geometrical (R element size) and electronic (R-T interactions) effects. The development devoted to the CeFeSi and ThCr2Si2- type solid solutions led us to the deterrnination of the magnetic phase diagrams of the systems La1-xYxMnSi and La1-xYxMn2Si2. We thus could specify the influence of the geometrical (dMn-Mn intraplane) and electronic factor (dMn-Si) on the magnetic behavior of manganese in these compounds characterized by manganese square planes. The magnetic study of the RMnX compounds with TiNiSi structure enabled us to extend our analysis to the other structural arrangements (infinite chains) of the manganese sublattice. Moreover, the evidence during this work of new high temperature TiNiSi-type structure form for ThMnSi and NdMnGe compounds, previously reported as isotypic of CeFeSi, allows us to compare the magnetic behavior of manganese sublattice in these two structural types for given R and T atoms. [...]
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Theses
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http://docnum.univ-lorraine.fr/prive/SCD_T_1999_0253_IJJAALI.pdf
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https://hal.univ-lorraine.fr/tel-01747277
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Submitted on : Thursday, March 29, 2018 - 10:56:28 AM
Last modification on : Monday, April 16, 2018 - 10:41:01 AM

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Ismaïl Ijjaali. Contribution à l'étude des propriétés structurales et magnétiques de siliciures et germaniures ternaires RTX, RTX2 et RT2X2 (R = La et lanthanoïdes ; T = Cr, Mn, Fe, Co). Autre. Université Henri Poincaré - Nancy 1, 1999. Français. ⟨NNT : 1999NAN10253⟩. ⟨tel-01747277⟩

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