Coordination Site Disorder in Spinel-Type LiMnTiO₄

LiMnTiO₄ was prepared through solid-state syntheses employing different heating and cooling regimes. Synchrotron X-ray and neutron powder diffraction data found quenched LiMnTiO₄ to form as single phase disordered spinel (space group <i>Fd</i>3̅<i>m</i>), whereas slowly cooled LiMnTiO₄ underwent partial phase transition from <i>Fd</i>3̅<i>m</i> to <i>P</i>4₃32. The phase behavior of quenched and slowly cooled LiMnTiO₄ was confirmed through variable-temperature synchrotron X-ray and neutron powder diffraction measurements. The distribution of Li between tetrahedral and octahedral sites was determined from diffraction data. Analysis of the Mn/Ti distribution in addition required Mn and Ti K-edge X-ray absorption near-edge structure spectra. These revealed the presence of Mn³⁺ in primarily octahedral and Ti⁴⁺ in octahedral and tetrahedral environments, with very slight variations depending on the synthesis conditions. Magnetic measurements indicated the dominance of antiferromagnetic interactions in both the slowly cooled and quenched samples below 4.5 K