Internal Structure and Magnetic Properties in Cobalt Ferrite Nanoparticles: Influence of the Synthesis Method

G. C. LAVORATO; LITTERST, F. JOCHEN; CONTRERAS, CYNTHIA; ALZAMORA, MARIELLA; BAGGIO-SAITOVITCH, ELISA

Montpellier

Conferencia; 5th Mediterranean Conference on the Applications of the Mössbauer Effect; 2019

The design of novel nanostructured magnetic materials requires a good understanding of the variation in the magnetic properties due to di¬erent synthesis conditions. Here we compare four di¬erent procedures for fabricating Co-ferrite nanoparticles with similar sizes between 7 and 10 nm (see Fig. 1), studying their structural and magnetic properties. Non-aqueous methods based on the thermal decomposition of metal acetylacetonates at high temperatures, either with or without surfactants, provide highly crystalline nanoparticles with large saturation magnetization values and a coherent reversal of the magnetic moment. However, we show that variations in the density of defects and in the shape of the nanocrystals can determine the distribution of switching fields and the effective magnetic anisotropy, which reaches up to ≈1x107 erg/cm3 for oleic acid-capped 9 nm nanoparticles. We found that the saturation magnetization values for nanoparticles produced by di¬fferent methods are in the range between 49 and 95 emu/g (see Fig. 2). Due to dif¬erences in the stoichiometry, in the cation occupancy, in the magnetic disorder and in the spin canting of the magnetic sub-lattices, the TD and SV samples are evaluated by in-field Mössbauer spectroscopy (Fig. 3). [1]In overall, by taking CoFe2O4 as a model system, our results indicate that the synthesis methods determine the magnetic response of ferrite nanoparticles with comparable size by promoting di¬fferences in their internal structure that govern the magnetization reversal process.[1] Gabriel Lavorato, et al. Part. Part. Syst. Charact. (2019), 1900061.