In-situ observation of the phase conditions of rare erath manganites controlled by structure and crystal structure and application of new properties

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We synthesized new rare-earth manganites, and analyzed new crystal structures and new properties.1. Study of new rare earth manganites with K_2NiF_4 structureNew phase of BaLnMnO4 (Ln = Nd, La) was obtained by annealing the single crystal (I4/mmm) in a reducing atmosphere. The structural change was caused by an oxygen deficiency, and a small amount of Mn^<2+> ions was formed by annealing in a reducing atmosphere. Na-oxide has a crystal structure with Fmmm symmetry, and La-oxide has Cccm symmetry.2. Study of new oxides with perovskite related structuresMany new phases have been synthesized and investigated their structures, electrical properties, thermal properties and magnetic properties. In the case of (A^<0.67>Ln^<0.33>)(Mn^<0.33>Ti^<0.67>)O_3 (Ln=rare earth, A=Ca, Sr), the electrical conductivity was closely related with structural parameters (Mn-O angles, Mn-O distances, ionic radii, t-factors, and coulomb potentials).3. In-situ observations of phase conditions at elevated temperatureWe found a first-order phase transition in BaLn_2Mn_2O_7 with a layered perovskite structure using a high-temperature TEM and XRD. The structure change was caused by a distortion of structure and change in electrical structure. In-situ observation by a high-temperature TEM was effective in order to know the structural change at real time. On the other hand, secondary-order phase transition was observed in perovskites with ABO_3 structure. The phase transition was caused by tilting of octahedra BO_6.