Effects of non magnetic aluminum Al doping on the structural, magnetic and transport properties in La0.57Nd0.1Sr0.33MnO3 manganite oxide

La0.57Nd0.1Sr0.33Mn1−xAlxO3 (LNSMAO) compounds were prepared for x = 0.0 to 0.3 by solid-state route. The X-ray powder diffraction has shown that all our synthesized samples are a single phase and have crystallized in the hexagonal symmetry with R 3¯ c space group. It is also worth mentioning that the unit cell volume decreases along with an increasing aluminum (Al) content. The scanning electron microscopy (SEM) has shown smooth and densified structures, clean and pure images. The magnetization and electrical measurements vs. temperature proved that all our samples exhibit a ferromagnetic to paramagnetic transition and a metallic to semiconductor one when the temperature increases. The substitution of Mn by aluminum (Al) leads to a continuous decrease of both the Curie temperature TC (from 342 K for x = 0.0 to 238 K for x = 0.3) and the resistivity transition temperature TP (from 338 K for x = 0.0 to 208 K for x = 0.3). When analyzing the electrical resistivity data, it has been concluded that the metallic (ferromagnetic) part of the resistivity (ρ) (below TP) can be explained by the following equation ρ = ρ0 + ρ2T2 + ρ4.5T4.5, signifying the importance of the grain/domain boundary, electron–electron and two magnon scattering processes. However, at a higher temperature (T > TP) the paramagnetic semiconducting regime, the adiabatic small polaron and Variable Range Hopping models are found to fit well.

► La0.57Nd0.1Sr0.33Mn1−xAlxO3 crystallize in the rhombohedral structure.
► The magnetization is governed by the DE interaction.
► The magnetization undergoes a strong decrease of TC.
► Metallic regime is emanated from the electron-(phonon, magnon) scattering processes.
► The electrical resistivity above TP is explained by Variable Range Hopping model.