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Nataša Jovic Orsini

Structural and Magnetic Anisotropy Effects on the Magnetic Hyperthermia Properties of Iron Oxide-based Nanoparticles

 During the work developed at the INA, different systems with specific stoichiometric compositions Zn_xFe_3-xO₄ and (Mn,Zn)_xFe_3-xO₄ were synthesized. By doping magnetite to obtain Zn_xFe_3-xO₄ with x < 0.4, we expect the increase in M_s and, thus the decrease in the anisotropy field of the material given by H_a = 2K_eff/M_s. This should allow us to perform heating experiments in biological media with high viscosity keeping large power absorption due to the Néel relaxation of magnetically soft material. All samples were synthesized using thermal decomposition method. Based on the literature, the incorporation of the Zn²⁺ ions into the spinel structure could be difficult when Zn(acac)₂ salt is used as a precursor. Therefore, we performed the synthesis using different precursors for Zn²⁺ ions, ZnCl₂ hydrate and Zn(acac)₂. Our goal was to overcome the problem with the particle size limitation when a classical protocols of the synthesis by the thermal decomposition method, which includes mixing of metal precursors, a solvent, surfactants and polyalcohol, has been used. Indeed, by changing the synthesis conditions we got mainly cubic, well crystallized nanoparticles with an average size above 16 nm. Following the classical protocol in the synthesis we obtained spherical nonoparticles with an average size around 10 nm. XRD, TEM (HRTEM), EDX, ATR-FTIR, SQUID and Mössbauer experimental techniques were used to characterize selected samples. XRD measurements point out on the presence of ZnO (~ 1 %) as impurity. ATR-FTIR measurements indicate that only small portion of OA is attached at the nanoparticles surface. EDX analysis shows the dopant ions content is smaller than it was expected. The preliminary measurements of hyperthermic capacity have been done under different experimental conditions and the results are promising. We plan to perform the ligand exchange protocol in order to transform nanoparticles into water and to examine their structural and magnetic features.

Poster/Oral presentation(s) /Conference abstract(s) originating from this mission