Structural and Magnetic Properties of Orthorhombic LixMnO₂
Rietveld refinement of the crystal and magnetic structures of LixMnO2 (x = 0.98, 1.00, 1.02) are performed using neutron and X-ray measurements. A significant structural disorder due to the presence of manganese ions in lithium positions (MnLi) and lithium ions in manganese ones (LiMn) is found to be a common feature of Li0.98MnO2, Li1.00MnO2, and Li1.02MnO2. An essential anisotropy of the thermal-expansion coefficients of the lithium manganese oxides is observed in the temperature range of 1.5-300 K. Furthermore, the distortion of the oxygen octahedral environment around the manganese ions decreases when the temperature lowers. This is attributed to the strong exchange interactions between parallel exchange-coupled Mn chains. First-principles calculations of the effective exchange-interaction parameters in Li16Mn16O32 confirm the essential antiferromagnetic interactions between the chains. In addition, a hypothetical (Li15Mn)Mn16O32 structure where a lithium atom located between the Mn double layers is replaced by a manganese atom is considered. The calculations reveal that the presence of such defects results in appearance of a ferromagnetic component that agrees with the magnetic measurements.
J. E. Medvedeva et al., "Structural and Magnetic Properties of Orthorhombic LixMnO₂," Solid State Sciences, Elsevier, Jan 2006.
The definitive version is available at http://dx.doi.org/10.1016/j.solidstatesciences.2006.11.013
Russian Foundation for Basic Research
Keywords and Phrases
X-Ray Diffraction; Exchange Parameter; First-Principles Calculation; Lithium Manganese Oxide; Magnetic susceptibility; Neutrons - Diffraction
Article - Journal
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