Phase and Structural Study of Self-Doped La 1-x-y Ca x O y MnO 3+δ
F. Figueiras a , J.P. Araujo b , V.S. Amaral a , P.B. Tavares c , A.B. Lopes d and J.M. Vieira d
a Departamento de Fisica and CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal
b Departamento de Fisica and IFIMUP, Universidade do Porto, 4169-007 Porto, Portugal
c Departamento de Quimica and Centro de Quimica --- Vila Real, Universidade de Trasos-Montes e Alto Douro, 5001-911 Vila Real, Portugal
d Departamento de Engenharia Ceramica e do Vidro and CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal
Full Text PDF
To understand the combined effect of divalent ion and A-site vacancy (O) self-doping, beyond the binary La 1-x MnO 3 system, polycrystalline La 1-x-y Ca x O y MnO 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 3 O 4 ) coexisting with the manganite phase. A small amount of perovskite related AMn 7 O 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.
DOI: 10.12693/APhysPolA.105.173
PACS numbers: 64.75.+g, 81.40.Rs, 75.50.--y, 72.20.My