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The influence of aluminum doping at Mn-site in La0.75Ca0.25MnO3 has been investigated, in the light of magnetotransport, and structural properties. As the aluminum concentration increases, the metal–insulator transition temperature (TP) decreases while activation energy in the insulating region (T>TP), resistivity and maximum value of magnetoresistance (MR) increases. The unit cell volume decreases slightly as the aluminum concentration increases. The observed results are analyzed in term of defect clustering due to aluminum doping at Mn-site induced random spin disorder and local strain and its effect on the magnetotransport properties.

The influence of transition element (TE) doping on the magnetotransport properties of ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ is studied for the entire transition element series ($\mathrm{T}\mathrm{E}=\mathrm{C}\mathrm{r},$ Fe, Co, Ni, Cu, Zn) for a fixed (5% at Mn sites) dopant concentration. The systematics of different properties such as the metal-insulator transition temperature ${T}_{p},$ the Curie temperature ${T}_{c},$ $\ensuremath{\rho}{(T}_{p}),\ensuremath{\rho}(5\mathrm{K}),$ and the maximum value of magnetoresistance (MR), with respect to lattice parameter and the ionic radii of dopants, are examined. The important findings include an interesting correlation between the maximum MR, the lattice parameter, and the ionic radii, and some distinct features exhibited by Fe, Cu, and Zn dopants.