Compressibilities of MnFe2O4 polymorphs

The high-pressure behavior and stability of synthetic jacobsite MnFe2O4 have been investigated up to 39.55 GPa at room temperature by means of in situ synchrotron X-ray diffraction using diamond anvil cell and multi-anvil high-pressure apparatus. The MnFe2O4 spinel undergoes a phase transition at about 18 GPa to form a denser antiferromagnetic CaMn2O4-type (CMafm) polymorph. The CMafm MnFe2O4 is stable up to 39.55 GPa in this study and remains after decompression. Fitting the pressure-volume data using a third-order Birch-Murnaghan equation of state, the isothermal bulk modulus values and the first pressure derivatives were obtained as K-0 = 169.7 (35) GPa, K-0' = 2.87 (40) for spinel-type MnFe2O4 and K-0 = 149.2 (24) GPa, K-0' = 3.98 (19) for CMafm MnFe2O4, respectively. If K-0' is fixed to 4, K-0 was obtained as 160.6 (11) GPa for spinel-type MnFe2O4 and 148.9 (7) GPa for CMafm MnFe2O4. The effects of cation substitution on the isothermal bulk modulus and pressure for phase transition of Fe3+-bearing spinels were discussed.