The average crystallite sizes calculated using Scherrer's formula (DXRD) and the W-H method (DW-H) ranged from 12 nm to 14 nm and from 12 nm to 18 nm, respectively (Table ). In all cases, the mean MNP diameters (DTEM) matched relatively well with the crystal sizes obtained from XRD using both methods, indicating a single-crystal structure. Although we did not observe a correlation between the Mn 2+ content and the crystallite size, similar results have been reported when using homogeneous samples in terms of size (∼6 nm in diameter), shape, and coating (only oleic acid) for MnxFe3-xO4, with x= 0.11 up to 0.49 . On the contrary, other works have reported an increase of the crystallite size for MnxFe3-xO4 MNPs obtained by a similar synthetic procedure but using 1-octadecene as a solvent or by co-precipitation in water using metallic chloride precursors, while a decrease of the crystallite size from 16.7 nm (x = 0) to 10.2 nm (x = 1) have been shown for Mn-doped CoFe2O4 ferrites . The origin of all these discrepancies could be attributed to defects frequently associated with the increase of Mn 2+ in the spinel structure, which could shrink the final structure. Under our synthetic procedure, the selection of BE instead of solvents like 1-octadecene that produce a very reducing ambient, could help in minimize crystal defects . Therefore, even when an increase in the Mn 2+ content raised strain defects, these were small enough and did not impact the final crystallite size of the systems.