Structural, thermal and magnetic properties of LiMnTiO4 spinel in different atmospheres

The thermal stability, phase transitions and magnetic behaviour of the LiMnTiO4 spinel have been investigated as a function of temperature and atmosphere (oxidizing or reducing) by means of thermogravimetry and in situ X-ray diffraction. This spinel undergoes interesting structural changes as a consequence of the stabilization of manganese in different oxidafion states, Mn3+, Mn3+/Mn2+, and Mn3+/Mn4+. Thermal treatments in air applied to the initial sample show a disorder-order transition (Fd3m-P4(3)32) that is related to the Mn3+/Mn2+ content in oxygen deficient phase, LiMnTiO4-delta. On treatment in oxygen rich atmosphere Mn4+ is Stabilized and titanium vacancies are produced, LiMnTi1-xO4. Magnetic properties are studied by magnetic susceptibility (DC) and magnetisation and the results can be interpreted on the basis of a spin glass state. This study contributes to a better understanding of the subtle structural and compositional variations shown by the title spinel as a function of the synthesis method employed. (c) 2008 Elsevier Masson SAS. All fights reserved.