LiMn₂O₄ low-temperature phase: synchrotron and neutron diffraction study

The structural evolution of LiMn₂O₄ spinel was followed from 320 K down to 10 K. The structural transformation, recently studied down to 230 K [Rodriguez-Carvajal, Rousse, Masquelier & Hervieu (1998). Phys. Rev. Lett. 81, 4660-4663], takes place near room temperature with a significant hysteresis: the high-temperature cubic phase transforms to a superstructure orthorhombic cell. The present study indicates that the nuclear structure is stable down to 10 K, while neutron diffraction patterns below 80 K show the rise of a magnetic ordering in the spinel phase. From Mn-O bond-length analysis of the MnO₆ octahedra, a temperature-independent charge ordering in the structure can be deduced.