Unexpectedly, the xEmpiric was similar to the theoretical one (xEmpiric = 1.40, Mn1.40Fe1.60O4), which could be related to samples where a fraction of Mn 2+ ions remain in a reduced phase such as manganowustite . As can be seen in Figure , all MNPs showed similar polyhedral morphologies and sizes between 13 and 15 nm (Table ), independently of the metallic precursors ratio or the solvent volume used, and in good agreement with previous works using the same precursors but different synthetic methods . As mentioned before, this is important to better correlate the effect that the composition plays on the magnetic, heating, and relaxivity properties, excluding the influence of other parameters such as size and shape. The use of BE resulted crucial, as depending on their iron chelation ability and boiling point, the use of other solvents can influence the final MNPs size, shape, and composition .