Effect of nominal strontium deficiency on the structure and the magnetic properties of La0.6Sr0.4−δMnO3 manganese perovskites

We have investigated the effect of nominal strontium deficiency on the structure and the magnetic properties of La0.6Sr0.4−δMnO3 (0 ≤ δ ≤ 0.3) manganese perovskites. The polycrystalline samples have been elaborated by the conventional ceramic method at 1573 K. The morphology, grain sizes and chemical analysis were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) techniques. The refinement of the structure by the Rietveld method revealed that most of these compounds crystallize in a rhombohedral (R3¯c) perovskite structure. Magnetization as a function of temperature, M(T), shows that these compounds exhibit a paramagnetic (PM) to ferromagnetic (FM) phase transition with decreasing temperature. The Curie temperature (TC) decreases from 361 K to nearly the room temperature (292 K) with decreasing nominal strontium content. In the paramagnetic region the inverse of the magnetic susceptibility was fitted by a Curie–Weiss law. Magnetization as a function of magnetic field, M(H), measured at 50 K shows that all compounds are FM with a maximum in the magnetic saturation moment for the nominal value δ = 0.12. A comparative analysis shows that nominal vacancies, δ, cannot generally be achieved by our conventional ceramic method and results in a shift of the perovskite manganite composition compensated by the formation of an additional Mn3O4 phase.