Synthesis,X-ray,magnetic and electrical studies of substituted (Pr,Sr)MnO3 perovskites

A systematic study of the structural, magnetic and electrical properties of the manganites Pr_1-x Sr _x MnO₃(0≤ x ≤ 0.5) has been carried out. X-ray diffraction investigation shows a structural change with composition, from orthorhombic (0 ≤ x ≤ 0.2) to rhombohedral (0.25 ≤ x ≤ 0.5). The magnetic properties of Pr_1-x Sr _x MnO₃ samples could be explained on the basis of a double exchange mechanism between pairs of Mn³⁺ and Mn⁴⁺ ions. These properties are strongly dependent on the ratio of Mn³⁺/Mn⁴⁺. The maximum of the ferromagnetic transition temperature T_c is reached at x ≈ 0.35 corresponding to a value 1.85 of this ratio. The investigation of the electrical properties shows a semiconductor to metal transition as a function of temperature (0.25≤x≤0.4) with a metallic-like behaviour above a critical temperature T_p . A semiconducting-like one is observed for all the range of temperature (50–300 K) for (0 ≤ x ≤ 0.2 and x = 0.5). The evolution of activated energies with the carrier concentration has been investigated.