Electrical transport and magnetoresistive properties of Nd-doped La_0.8Sr_0.2MnO₃ ceramics

In this paper, La_0.8−xNd_xSr_0.2MnO₃ (x = 0.03, 0.04, 0.05, and 0.06) ceramics were synthesized by a sol–gel method. The structure, surface morphology, electrical transport, and magnetoresistive properties of these materials were studied. X-ray diffraction (XRD) revealed samples to be single-phase with a distorted perovskite structure belonged to the (\({\text{R}}\bar 3{\text{c}}\)) space group. Scanning electron microscopy (SEM) revealed the samples to contain compact grains, with the grain size increasing slightly with the amount of doping Nd³⁺. The standard four-probe method was used to test the electrical resistivity of the samples as a function of temperature (ρ–T). The metal–insulator transition temperature (T_p) shifted to lower temperatures and the resistivity (ρ) increased with the content of Nd³⁺. Peak temperature coefficient of resistance (TCR) and magnetoresistance (MR) were both affected by the Nd³⁺ substitution. At x = 0.05, peak TCR and MR reached 5.12% K⁻¹ and 19.78%, respectively. The mechanism responsible for both electrical and magnetoresistive properties of these materials was discussed in the frame of double-exchange (DE) interaction.