Stability of the layered Sr<sub>3</sub>Ti<sub>2</sub>O<sub>7</sub> structure in La<sub>1.2</sub>(Sr<sub>1-x</sub>Ca<sub>x</sub>)<sub>1.8</sub>Mn<sub>2</sub>O<sub>7</sub>
R Ganguly; V Siruguri; I K Gopalakrishnan; J V Yakhmi
Журнал:
Journal of Physics: Condensed Matter
Дата:
2000-02-28
Аннотация:
Samples with nominal compositions La<sub>1.2</sub> (Sr<sub>1-x </sub> Ca<sub>x </sub> )<sub>1.8</sub> Mn<sub>2</sub> O<sub>7</sub> (x = 0.00, 0.25, 0.50, 0.65, 0.80 and 1.00) have been prepared and characterized by x-ray diffraction (XRD) and ac susceptibility techniques. Drastic changes in the XRD pattern and in the ac susceptibility versus temperature behaviour at x = 0.65 indicate that single phase compounds with layered Sr<sub>3</sub> Ti<sub>2</sub> O<sub>7</sub> structure are formed only up to x = 0.50. Rietveld refinement of the XRD patterns of x = 1.00 composition suggests that the compositions with x 0.65 form multiphase mixtures comprising hole doped perovskite manganates as majority phases and CaO as the minority phase. These results are at variance with the literature reports that the compound La<sub>1.2</sub> Ca<sub>1.8</sub> Mn<sub>2</sub> O<sub>7</sub> forms with layered Sr<sub>3</sub> Ti<sub>2</sub> O<sub>7</sub> structure.
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