MnO·Mn2O3 Manganese(II,III) oxide is the chemical compound with formula Mn3O4.

[3] Considerable research has centred on producing nanocrystalline Mn3O4 and various syntheses that involve oxidation of MnII or reduction of MnVI.

[4][5][6] Mn3O4 has been found to act as a catalyst for a range of reactions e.g. the oxidation of methane and carbon monoxide;[7][8] the decomposition of NO,[9] the reduction of nitrobenzene[10] and the catalytic combustion of organic compounds.

[3] At room temperature Mn3O4 is paramagnetic, below 41-43 K, it is ferrimagnetic[12] although this has been reported as reducing in nanocrystalline samples to around 39 K.[13] Mn3O4 is sometimes used as a starting material in the production of soft ferrites e.g. manganese zinc ferrite,[14] and lithium manganese oxide, used in lithium batteries.

[15] Manganese tetroxide can also be used as a weighting agent while drilling reservoir sections in oil and gas wells.