High-pressure stability of the tetragonal spinel MgMn2O4:: Role of inversion -: art. no. 174102

The phase stability of the MgMn2O4 spinel has been studied by means of high-pressure x-ray diffraction for pressures up to 30 GPa. Two samples with different inversion degrees have been considered. Both spinels undergo a phase transition toward an orthorhombic structure (CaMn2O4 type). As for the more inverted sample the transition pressure is at least I GPa lower than that of the less inverted spinel, and the volume contraction, relative compressibility, and density trends are different for the two samples, as well. These variations have been explained considering the differences in the cation distribution and electronic proprieties. Besides, a general scheme for the behavior of tetragonal spinel manganites at high pressure is suggested.