  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 towards an orthorhombic structure (CaMn2O4-type). For the more
inverted sample the transition pressure is at least 1 GPa lower with respect to
that of the less inverted spinel. Also the volume contraction, relative
compressibility and density trends are different for the two samples. These
variations have been explained according to differences in the cation
distribution. and electronic properties of the samples.
