Abstract This report presents the structural, magnetoresistance, electrical and thermal transport properties of Aluminium substituted La 0.7 Ba 0.3 Mn 1−x Al x O 3 (0 ≤ x ≤ 0.15) compounds synthesized by solid state reaction method. To obtain crystallographic parameters, the X-ray diffraction patterns are fitted in R-3c space group with Rietveld refinement method. The resistivity and magneto-transport measurements are performed using standard four-probe assembly with and without magnetic fields. The peak resistivity ρ peak is noted at Metal-Insulator Transition temperature ( T MI ) and lowering in T MI is observed for higher concentrations of Al 3+ . The resistivity data have been analyzed in two parts. Firstly, in the metallic region below T MI the resistivity data is fitted with three degree polynomial. Secondly, in the semiconducting region above T MI data have been fitted with Variable Range Hopping (VRH) and Small Polaron Hopping (SPH) models. The Seebeck coefficients found to be positive throughout the temperature range (10 K–300 K) with holes as dominating charge carriers. Similar to the resistivity profile, in metallic region the thermo-power is explained with qualitative model based on diffusion, magnon-drag, phonon-drag and spin fluctuation contributions whereas the semiconducting region is explained with small polaron hopping model.

中文翻译：

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Al掺杂对La0.7Ba0.3Mn1-xAlxO3(0≤x≤0.15)锰酸盐磁阻和输运性能的影响

摘要 本报告介绍了通过固态反应法合成的铝取代 La 0.7 Ba 0.3 Mn 1-x Al x O 3 (0 ≤ x ≤ 0.15) 化合物的结构、磁阻、电和热传输性能。为了获得晶体学参数，使用 Rietveld 精修方法将 X 射线衍射图拟合到 R-3c 空间群中。电阻率和磁传输测量是使用标准的四探头组件在有和没有磁场的情况下进行的。在金属-绝缘体转变温度 (T MI ) 处注意到峰值电阻率 ρ 峰，并且对于较高浓度的 Al 3+ 观察到 T MI 降低。电阻率数据分两部分进行分析。首先，在低于 T MI 的金属区域，电阻率数据用三阶多项式拟合。第二，在 T MI 数据上方的半导体区域中，已经拟合了可变距离跳跃 (VRH) 和小极化子跳跃 (SPH) 模型。发现塞贝克系数在整个温度范围 (10 K–300 K) 内为正，空穴作为主要电荷载流子。与电阻率分布相似，在金属区域，热功率用基于扩散、磁子阻力、声子阻力和自旋波动贡献的定性模型解释，而半导体区域用小极化子跳跃模型解释。