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Phase and Structural Study of Self-Doped La_{1-x-y}Ca_xØ_yMnO_{3+δ}

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Figueiras F., Araújo J., Amaral V., Tavares P., Lopes A., Vieira J.

Acta Physica Polonica A

2004

vol. 105

issue 1-2

173-182

To understand the combined effect of divalent ion and A-site vacancy (Ø) self-doping, beyond the binary La_{1-x}MnO_3 system, polycrystalline La_{1-x-y}Ca_xØ_yMnO_{3+δ} samples were studied. Samples with Ca substitution and excess Mn in the range x<0.33 and y<0.45, respectively, were prepared by standard solid-state reactions. Structural and phase analysis of the samples were done by X-ray diffraction and transmission electron microscopy. The manganite structure in this composition range includes rhombic and orthorhombic phases. Most samples contain the hausmanite phase (Mn_3O_4) coexisting with the manganite phase. A small amount of perovskite related AMn_7O_{12} (A=La,Ca) structure near the hausmanite-manganite boundary is also found in samples treated in oxygen atmosphere. The calculated vacancy content accommodated in the manganite phase can be higher than 1/8, the reported limit for La_{1-x}MnO_3, which is confirmed in our x=0 sample. For the compositions studied, a ferromagnetic metallic behavior below T_C is found, confirming the stability of the Mn sublattice, and near the optimum stoichiometric ((x=0. 33, y=0) system, a net A-site vacancy content (up to y=0.2) does not degrade the magnetic and electric properties.

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1 Acta Physica Polonica A

1 2004

1 Amaral V.

1 Araújo J.

1 Figueiras F.

1 Lopes A.

1 Tavares P.

1 Vieira J.

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Phase and Structural Study of Self-Doped La_{1-x-y}Ca_xØ_yMnO_{3+δ}