Thermal decomposition of acetylacetonates for highly reproducible synthesis of M-ferrite (Mn, Co and Zn) nanoparticles with tunable magnetic properties

Abstract

In this work, we evaluated two synthetic approaches for the synthesis of M-ferrites nanoparticles, where M = Mn, Co, Zn with desired stoichiometric composition. As a starting point, thermal decomposition of acetylacetonates in benzyl alcohol and benzyl ether with oleic acid was chosen. Both of these approaches are widely used for the preparation of iron oxide nanoparticles; however, the synthesis of M-ferrites nanoparticles using these approaches is not well described. We have studied the influence of the nature of the solvent and surfactant on the quality of obtained ferrites (stoichiometric M:Fe ratio, structural phase analysis, morphology and core size of nanoparticles). It was shown that the chemical structure of solvent and presence of oleic acid plays a key role in controlling the nanoparticles stoichiometry. When benzyl alcohol was used as solvent, M-ferrites nanoparticles with diameters ranging from 3 to 5 nm were obtained, whereas of the benzyl ether with oleic acid resulted in formation of nanoparticles with diameters ranging from 7 to 9 nm. Moreover, only thermal decomposition of M acetylacetonates in benzyl alcohol was successful in obtaining M-ferrites nanoparticles with desired stoichiometry and high reproducibility M:Fe = 1:2 ± 0.1). In addition, magnetic properties of obtained nanoparticles have been studied at room temperature and their dependence on M:Fe ratio (1:2, 1:6, 1:10) was shown. The results show a superparamagnetic behavior for all synthesized samples and high magnetization values from 19.7 to 99.3 A•m2•kg−1. The maximum values of magnetization of M-ferrites samples are quite high for such small nanoparticles, which are closely related to their high crystallinity.