Colossal magnetoresistance study in nanophasic La0.7Ca0.3MnO3 manganite
Colossal magnetoresistance study in nanophasic La0.7Ca0.3MnO3 manganite
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DOI：
10.1088/0022-3727/39/1/003
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发表时间：
2005-05
期刊：
影响因子：
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通讯作者：
P. K. Siwach;U. K. Goutam;P. Srivastava;H. Singh;R. S. Tiwari;O. Srivastava
中科院分区：
文献类型：
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作者：
P. K. Siwach;U. K. Goutam;P. Srivastava;H. Singh;R. S. Tiwari;O. Srivastava
在这项研究中，我们报告的低场磁输运性能的La0.7Ca0.3MnO3通过聚合物前驱体路线合成的烧结温度的影响。在600 °C（S6）、700 °C（S7）、800 ° C（S8）、900 ° C（S9）和1000 °C（S10）下烧结La0.7Ca0.3MnO3。X射线衍射证实相形成在600 °C开始。所有样品都是单相的，具有正交晶胞。随着烧结温度的降低，晶格常数减小.微晶以及晶粒尺寸也表现出强烈的烧结温度依赖性。所有样品都具有特征的绝缘体-金属（TIM）以及顺磁-铁磁（PM-FM）（TC）转变。TC随烧结温度的变化范围很小[272-256 K]，而TIM则从267 K（S10）下降到138 K（S6），大幅降低了129 K。这种TC-TIM差异是由于这样的事实，而前者是一个内在的特性，后者强烈地依赖于外在因素，如合成条件，晶界和相关的障碍。对于所有的样品的磁阻（MR）表现出强烈的依赖于TS。MR增加降低温度以及增加与TC周围发生的本征贡献的字段。所有样品的MR的这些变化已被解释的微观结构的变化和自旋极化隧道在低温下。
In this study we report the effect of sintering temperature on the low field magnetotransport properties of La0.7Ca0.3MnO3 manganite synthesized through the polymeric precursor route. The La0.7Ca0.3MnO3 has been sintered at 600 °C (S6), 700 °C (S7), 800 °C (S8), 900 °C (S9) and 1000 °C (S10). X-ray diffraction confirms that phase formation starts at 600 °C. All the samples are single phasic having an orthorhombic unit cell. The lattice parameters decrease on lowering the sintering temperature (TS). The crystallite as well as the grain size also show strong dependence on the sintering temperature. All the samples possess characteristic insulator–metal (TIM) as well as paramagnetic–ferromagnetic (PM–FM) (TC) transitions. The TC varies in a small range [272–256 K] as a function of sintering temperature whereas the TIM goes down from 267 K (S10) to 138 K (S6), a strong decrease of 129 K. This TC–TIM discrepancy is due to the fact that whereas the former is an intrinsic characteristic, the latter depends strongly on the extrinsic factors e.g. synthesis conditions, grain boundaries and associated disorders. For all the samples magnetoresistance (MR) shows strong dependence on TS. The MR increases on lowering the temperature as well as on increasing the field with the occurrence of an intrinsic contribution around TC. These variations of MR for all the samples have been explained in terms of the microstructural variations and spin-polarized tunnelling at low temperatures.