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

Abstract

The design of novel nanostructured magnetic materials requires a good understanding of the variation in the magnetic properties due to different synthesis conditions. In this work, four different procedures for fabricating Co‐ferrite nanoparticles with similar sizes between 7 and 10 nm are compared by 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, variations in the density of defects and in the shape of the nanocrystals determine the distribution of switching fields and the effective magnetic anisotropy, which reaches up to ≈1 × 107 erg cm−3 for oleic acid‐capped 9 nm nanoparticles. It is shown that the saturation magnetization values for nanoparticles produced by different methods are in the range between 49 and 95 emu g−1 due to differences in the stoichiometry, in the cation occupancy, in the magnetic disorder and in the spin canting of the magnetic sub‐lattices, the latter evaluated by in‐field Mössbauer spectroscopy.

Synthesis, Characterization and Magnetic Hyperthermia of Monodispersed Cobalt Ferrite Nanoparticles for Cancer Therapeutics

“…No evident traces of FeO or CoO were detected, as no exchange bias was noticed in Figure 4 C,D. CFNPs displayed the higher coercive field (H C ) at 20 K, exhibiting a value around 1.349 T ( Figure 4 B), thus confirming the presence of highly crystalline Co x Fe 3-x O 4-δ nanoparticles prepared by thermal decomposition [ 48 , 49 , 50 ]. The reduced remnant magnetization (M R /M S ) of CFNP is 0.86, a signature value for a system with cubic anisotropy [ 51 ].…”

Hybrid magnetic nanoparticles as efficient nanoheaters in biomedical applications

“…Structural defects are ubiquitous in nanostructures 74,75,[165][166][167][168] and can have a strong impact on the spin arrangement and magnetization reversal. For example, Fe 3 O 4 MNPs obtained by different synthesis routes exhibited anti-phase boundaries, 165,169 which are detrimental to the heating efficiency since they are responsible for a reduction in the magnetic moment.…”

Highly Efficient T2 Cobalt Ferrite Nanoparticles Vectorized for Internalization in Cancer Cells

“…The larger the size and the M s value, the higher the r 2 relaxivity of the NPs [ 6 ]. Changes in the magnetic properties of the NPs are also observed depending on the synthesis method used [ 7 , 8 ]. These differences are mainly attributed to changes in the crystallographic order of the material or the presence of impurities.…”