Influence of Sr²⁺ substitution at Ca site of divalent-doped La0.5Ca0.5-xSrxMnO3 (x = 0, 0.10, 0.20) manganite on electrical resistivity and magnetoresistance

Manganites with the general formula La1-xAxMnO3 (A = Ca and Sr) are well known for their colossal magnetoresistance effect, where a material’s resistivity changes drastically under a magnetic field. This property makes them promising candidates for magnetic sensors and spintronic applications. The effect of Sr substitution at the Ca site in La0.5Ca0.5-xSrxMnO3 (x = 0, 0.10, 0.20) manganites on electrical resistivity and magnetoresistive properties was studied. The samples were prepared using a solid-state reaction technique, which involved the sequential processes of weighing, grinding, calcination, pelletizing, and sintering. The electrical resistivity of the samples was measured using the four-point probe technique over a temperature range of 30 K to 300 K, under applied magnetic fields of 0 T and 0.8 T. The measurements revealed a metal-insulator transition (MI) in all samples. The transition temperature (TMI) decreased with increasing Sr content. Specifically, at 0 T, the TMI shifted from 110 K (x = 0) to 54 K (x = 0.20), and the overall resistivity decreased significantly with increasing Sr concentration. In addition, an enhanced magnetoresistance (MR) effect was observed for the x = 0.20 sample, which is attributed to spin-dependent interfacial tunneling enhanced under a low magnetic field of 0.8 T. The magnetoresistance peaked at x = 0 and decreased progressively with further Sr doping, likely due to stabilized ferromagnetic ordering. This stabilization led to a reduction in the rate of eg electron hopping and elongation of the Mn-O bond length, thereby weakening the double exchange mechanism. This study is significant as it highlights the impact of A-site cation substitution on the structure property relationships in manganites. As potential candidates for magnetoresistance and spintronic applications, the results demonstrate that Sr2+ substitution effectively modifies the electrical properties of La-based manganites.