Structural and magnetic properties of the iron substituted lithium–manganese spinel oxides

Most studies on the lithium–manganese oxide as a cathode material have concentrated on the stabilization of the cubic spinel structure, mainly by doping other transition metal ions into LiMn2O4 lattice. Partial substitution of Fe3+ ions for Mn3+ restrains the Jahn–Teller effect, owing to the reduction of Mn3+/Mn4+ ratio. In LiFe0.1Mn1.9O4 spinel oxide the phase transitions from cubic to orthorhombic and/or tetragonal structure, appearing for LiMn2O4 below the room temperature, may be totally suppressed. The changes in stoichiometry of LiFexMn2−xO4 system, modify the sequence of phase transitions and lower the transition temperature. A superexchange magnetic interaction between the Mn ions via oxygen atoms alters, with the Fe3+-content in LixMn3−xO4 increasing from x=0.0–0.1x=0.0–0.1, showing the antiferromagnetic ordering at very low temperature. The Néel point increases from 7 to 27 K. Effect of Fe3+ ions substitution in the LiFexMn2−xO4 system on its low-temperature structural phase transitions, have been investigated using high-resolution synchrotron X-ray powder diffraction, neutron powder diffraction and the magnetic susceptibility measurements. Divergences appear in the interpretation of magnetic structure on the basis of experimental results, acquired from neutron diffraction data, and obtained from the direct current susceptibility measurements.

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