Structural and Magnetic Properties of La1−x(Ca,Sr)xMnO3 Powders Produced by the Hydrothermal Method

La1−x(Ca,Sr)xMnO3 manganites have been produced using the hydrothermal method. The influence of the concentration of La, Ca, and Sr on the structural, morphological, and magnetic properties was studied and analyzed. The X-ray diffraction analysis showed that samples crystallized in rhombohedral or trigonal symmetries depending on the stoichiometry. The morphological analyses obtained by using scanning electron microscopy showed cauliflower-type microstructures in all samples. Energy-dispersive spectroscopy studies were also performed, evidencing not only the presence of the constituent elements but an oxygen deficiency and manganese-relative excess in all the samples. This fact is suggested as the cause of the unusual magnetic behavior where a low-temperature re-entrant phase was observed within the ferromagnetic matrix in some of the samples attributed to spin frustration. Furthermore, for some samples, a critical Curie temperature higher than the reported values is attributed to the relative excess of manganese ions, which can occupy other sites in the lattices as interstices or La, Ca, and Sr sites.