LaMnO3 often has lanthanum vacancies as evidenced by neutron scattering. For this reason, this material is usually referred as LaMnO3+ẟ. These vacancies generate a structure with a rhombohedral unit cell in this perovskite. A temperatures below 140 K, this LaMnO3+ẟ semiconductor exhibit a ferromagnetic order.[3]
Synthesis
Lanthanum manganite can be prepared via solid-state reactions at high temperatures, using their oxides or carbonates.[4] An alternative method is to use lanthanum nitrate and manganese nitrate as raw materials. The reaction occurs at high temperature after the solvents are vaporized.[5]
In lanthanum manganite, both the La and the Mn are in the +3 oxidation state. Substitution of some of the La atoms by divalent atoms such as Sr or Ca induces a similar amount of tetravalent Mn4+ ions. Such substitution, or doping can induce various electronic effects, which form the basis of a rich and complex electron correlation phenomena that yield diverse electronic phase diagrams in these alloys.[6]
^Liu, Yuxi; Dai, Hongxing; Du, Yucheng; Deng, Jiguang; Zhang, Lei; Zhao, Zhenxuan; Au, Chak Tong (2012). "Controlled preparation and high catalytic performance of three-dimensionally ordered macroporous LaMnO3 with nanovoid skeletons for the combustion of toluene". Journal of Catalysis. 287: 149–160. doi:10.1016/j.jcat.2011.12.015. ISSN0021-9517.
