Mn(I) in an extended oxide: The synthesis and characterization of La1–xCaxMnO2+∂ (0.6 ≤ x ≤ 1)
E Dixon, J Hadermann, S Ramos, A L Goodwin and M A Hayward
J Am Chem Soc 133, 18397 (2011)
Reduction of La1–xCaxMnO3 (0.6 ≤ x ≤ 1) perovskite phases with sodium hydride yields materials of composition La1–xCaxMnO2+δ. The calcium-rich phases (x = 0.9, 1) adopt (La0.9Ca0.1)0.5Mn0.5O disordered rocksalt structures. However local structure analysis using reverse Monte Carlo refinement of models against pair distribution functions obtained from neutron total scattering data reveals lanthanum-rich La1–xCaxMnO2+δ (x = 0.6, 0.67, 0.7) phases adopt disordered structures consisting of an intergrowth of sheets of MnO6 octahedra and sheets of MnO4 tetrahedra. X-ray absorption data confirm the presence of Mn(I) centers in La1–xCaxMnO2+δ phases with x < 1. Low-temperature neutron diffraction data reveal La1–xCaxMnO2+δ (x = 0.6, 0.67, 0.7) phases become antiferromagnetically ordered at low temperature.