Well-dispersed, ultrasmall, superparamagnetic magnesium ferrite nanocrystallites with controlled hydrophilicity/hydrophobicity and high saturation magnetization

A facile approach was developed to create well-dispersed, ultrasmall superparamagnetic magnesium ferrite nanocrystallites with controlled hydrophilicity/hydrophobicity and high saturation magnetization by a room temperature precipitation reaction followed by a solvent thermal process at low temperature. The in situ NaCl cage'' which self-formed during the room temperature precipitation reaction confined the formation, crystallization, and growth of the magnesium ferrite nanocrystallites, resulting in an ultrasmall average particle size of similar to 3.7 nm, while a high saturation magnetization comparable with that of the bulk MgFe2O4 material was achieved with a low Mg2+ content of similar to 10%. The surfaces of these superparamagnetic magnesium ferrite nanocrystallites could be modified with oleic acid/citric acid ester coatings to have controlled hydrophobicity/hydrophilicity to ensure their good dispersion in either nonaqueous or aqueous environments. This approach could be readily applied to other ferrite material systems and promises a wide range of technical applications.