Abstract The influence of A-site cation disorder of monovalent alkali ions on structural and magneto-transport properties of colossal magnetoresistive (CMR) materials has been reported. All the compounds crystallize in Pbnm space group with orthorhombic symmetry. At low temperature, the samples exhibit a paramagnetic (PM) to ferromagnetic (FM) transition and a semiconductor to metallic one. The variation in both Curie temperature (Tc) and metal-semiconductor transition temperature (TMS) can be explained by the change in Mn4+ content and average A-site cation radius. A decrease in resistivity in the vicinity of TMS has been observed with an increase in the applied magnetic field. The values of Tc are close to TMS, signifying strong correlations between the magnetic and electrical properties. The electrical resistivity data in paramagnetic-semiconducting region (T > TMS) may be described by the adiabatic small polaron hopping (ASPH) model. Maximum magnetoresistance (MR%) has been observed in the vicinity of TMS.

中文翻译：

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La0.5Nd0.15Ca0.25A0.1MnO3 (A = Ca, Li, Na, K) CMR 锰酸盐中的高磁阻：它们的磁和电特性之间的相关性

摘要 已经报道了单价碱离子的 A 位阳离子无序对巨磁阻 (CMR) 材料的结构和磁传输性能的影响。所有化合物均以正交对称的Pbnm空间群结晶。在低温下，样品表现出顺磁 (PM) 到铁磁 (FM) 的转变以及半导体到金属的转变。居里温度 (Tc) 和金属-半导体转变温度 (TMS) 的变化可以通过 Mn4+ 含量和平均 A 位阳离子半径的变化来解释。随着外加磁场的增加，观察到 TMS 附近的电阻率降低。Tc 的值接近 TMS，表明磁和电特性之间有很强的相关性。顺磁-半导体区域（T > TMS）的电阻率数据可以用绝热小极化子跳跃（ASPH）模型来描述。在 TMS 附近观察到最大磁阻 (MR%)。