Impact of the sintering temperature on the structural, magnetic and electrical transport properties of doped La_0,67Ba_0,33Mn_0,9Cr_0,1O₃ manganite

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• 作者：Marwè ; ne Oumezzine^a ; ^b ; ^{Oumezzine@hotmail.co.uk} ; ^{marouan.omezzine@etudiant.univ-rennes1.fr} ; Octavio Pe&ntilde ; a^b ; Thierry Guizouarn^b ; Ronan Lebullenger^b ; Mohamed Oumezzine^a
• 关键词：Perovskite manganite ; Sintering temperature ; Electrical transport ; Curie temperature
• 刊名：Journal of Magnetism and Magnetic Materials
• 出版年：2012
• 期刊代码：31_03048853
• 类别：ph
• 出版时间：September, 2012
• 卷：324
• 期：18
• 页码：2821-2828
• 文件大小：868 K

摘要

A systematic investigation of the La₀,₆₇Ba₀,₃₃Mn₀,₉Cr₀,₁O₃ perovskite has been undertaken, mainly to understand the impact of the sintering temperature on the structural, microstructural, magnetic and electrical transport properties in these materials. The La₀,₆₇Ba₀,₃₃Mn₀,₉Cr₀,₁O₃ manganite was sintered by a solid-state route at 1000 掳C, 1200 掳C and 1400 掳C. The X-ray diffraction studies show that all samples crystallize with the rombohedral symmetry within the space group RC, regardless of the sintering temperatures employed in this work. The Mn顥窸顥窶n bond angle decreases and the Mn顥窸 bond length increases with the increase of the grain size. All samples undergo a paramagnetic (PM)-ferromagnetic (FM) phase transition at T=T_C. Both the magnetization and the Curie temperature T_C decrease with increasing grain size mainly due to the increase of the Mn顥窸 bond length d_Mn顥窸. The electrical resistivity (蟻) increases with decreasing grain size because of the enhancement of the grain boundary effect. Low temperature resistivity data below T_C was fitted by the relation 蟻=蟻₀+蟻²T²+蟻^4.5T^4.5, indicating the importance of the grain/domain boundary, the electron-electron scattering effects and, to a lesser extent, the electron-(magnon,phonon) scattering effects in the mechanism of conduction. On the other hand, the high temperature resistivity above the metal-insulator (M-I) transition T_p for the sample sintered at 1000 掳C was explained using variable range hopping (VRH) and small polaron hopping (SPH) models. IR studies revealed that the vibration mode at 411 cm^鈭?, associated with the internal bending of MnO₆ octahedra, becomes softer, indicating an increase of the distortion.