Electrical conductivity and low field magnetoresistance in polycrystalline La1-xKxMnO3 pellets prepared by pyrophoric method
Electrical conductivity and low field magnetoresistance in polycrystalline La1-xKxMnO3 pellets prepared by pyrophoric method
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DOI：
10.1016/j.ssc.2005.01.023
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发表时间：
2005-06-01
影响因子：
2.1
通讯作者：
Dey, TK
中科院分区：
文献类型：
--
作者：
Das, S;Dey, TK
一系列用自燃法制备的单价 (K) 掺杂 La1-xKxMnO3 多晶颗粒的电导率和磁阻已被报道。 K 掺杂提高了系统的电导率和居里温度 (T-C)。随着 K 含量的增加，居里温度从 260 K 增加到 309 K。在金属-绝缘体转变温度 (T > T-MI) 之上，电阻率由绝热极化模型主导，而在铁磁区域 (50 < T < T-MI)，电阻率由多个电子散射过程控制。基于掺杂锰酸盐由相分离的铁磁金属和顺磁绝缘区域组成的情况，通过单个表达式可以很好地描述电阻率在大约 50 到 300 K 之间的温度变化的所有特征。所有 K 掺杂样品都清楚地显示出强场相关电阻率最小值接近 30 K 的存在。反铁磁耦合晶粒之间的电荷载流子隧道效应很好地解释了单价 (K) 掺杂镧锰酸盐中的电阻率最小值。基于晶界处自旋极化隧道的现象学模型很好地解释了低于 T-C 的各种温度下磁阻的场依赖性。还估计了 DE 机制产生的本征部分以及源自晶间自旋极化隧道效应的部分的贡献。 (c) 2005 Elsevier Ltd. 保留所有权利。
Electrical conductivity and magnetoresistance of a series of monovalent (K) doped La1-xKxMnO3 polycrystalline pellets prepared by pyrophoric method have been reported. K doping increases the conductivity as well as the Curie temperature (T-C) of the system. Curie temperature increases from 260 to 309 K with increasing K content. Above the metal-insulator transition temperature (T > T-MI), the electrical resistivity is dominated by adiabatic polaronic model, while in the ferromagnetic region (50 < T < T-MI), the resistivity is governed by several electron scattering processes. Based on a scenario that the doped manganites consist of phase separated ferromagnetic metallic and paramagnetic insulating regions, all the features of the temperature variation of the resistivity between similar to 50 and 300 K are described very well by a single expression. All the K doped samples clearly display the existence of strongly field dependent resistivity minimum close to similar to 30 K. Charge carrier tunneling between antiferromagnetically coupled grains explains fairly well the resistivity minimum in monovalent (K) doped lanthanum manganites. Field dependence of magnetoresistance at various temperatures below T-C is accounted fairly well by a phenomenological model based on spin polarized tunneling at the grain boundaries. The contributions from the intrinsic part arising from DE mechanism, as well as, the part originating from intergrannular spin polarized tunneling are also estimated. (c) 2005 Elsevier Ltd. All rights reserved.