Facile Synthesis, Magnetic and Electric Characterization of Mixed Valence La0.75K0.25AMnTiO6 (A = Sr and Ba) Perovskites.

A new series of mixed valence perovskites, La0.75K0.25AMnTiO6 (A = Sr and Ba) nanocubes, have been synthesized by a mild hydrothermal route. From powder X-ray diffraction (XRD) analysis, the crystal structure of La0.75K0.25AMnTiO6 was solved as the orthorhombic symmetry (space group Pbnm) with a random A-site or B-site arrangement. The phase purity of the products was confirmed by ICP, SEM, and EDS analyses, and the oxidation states of the B-site metal atoms were determined to be +4 for Ti and +3/+4 for Mn from XPS results. The soft ferromagnetic behavior is present in both samples. The Curie point TC has been detected as high as 309 K in La0.75K0.25SrMnTiO6 and 217 K in La0.75K0.25BaMnTiO6. A Griffiths phase can be observed at the high temperature region, which is related to the magnetic inhomogeneity induced by the existence of short-range ferromagnetic clusters. The resistivity measurements indicate that the semiconducting properties of the samples can be depicted better by variable range hopping (VRH) due to a diluted double-exchange interaction of Mn3+-O-Mn4+ with Ti4+ doping.