Microstructure and magnetocaloric effect in Gd₅Si₂(Ge_1−xGa_x)₂ alloys

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• 作者：D.M. Raj Kumar ; M. Manivel Raja ; R. Gopalan ; R. Balamuralikrishnan ; A.K. Singh ; V. Ch ; rasekaran
• 关键词：Gd– ; Si– ; Ge– ; Ga alloys ; Microstructure ; Structural and magnetic transitions ; Magnetocaloric effect
• 刊名：Journal of Alloys and Compounds
• 出版年：2008
• 期刊代码：45_09258388
• 类别：ms
• 出版时间：11 August 2008
• 卷：461
• 期：1-2
• 页码：14-20
• 文件大小：1003 K

摘要

Crystal structure of the phases, microstructure and magnetocaloric effect were investigated in Gd₅Si₂(Ge_1−xGa_x)₂ alloys with x = 0, 0.01, 0.02 and 0.03. The phase identification and compositional analysis were carried out by a combination of X-ray diffraction, scanning electron microscopy and electron probe micro-analysis. The Gd₅Si₂Ge₂-type matrix phase having an orthorhombic structure co-exists with Gd₅Ge₃-type and GdGe-rich phases. Ga was found to have preferentially partitioned to the orthorhombic Gd₅Si₂Ge₂-type matrix phase. Magneto-structural transition temperatures determined from differential scanning calorimetry and thermo-magnetic techniques revealed that Ga substituted alloys exhibit only magnetic transition unlike parent Gd₅Si₂Ge₂ alloy which displays both structural and magnetic transitions. A maximum magnetic entropy change (ΔS)_M of 7.0 J/kg K was obtained in x = 0 alloy for a magnetic field change of 2 T and its magnitude was lower in the Ga substituted alloys.