Structural and Magnetic Properties of Bottom-up Synthesized ZnFe₂O₄ Nanoparticles

Abstract

Zinc ferrite nanoparticles are bottom-up synthesized and then peptized in aqueous media resulting in stable magnetic fluids. X-ray powder patterns are analyzed using Rietveld structure refinement and indicate the existence of cation inversion at the sites of the spinel-type nanocrystal. Magnetic and magneto-optical properties therefore arise and are investigated by static measurements performed on individual particles solutions.

Synthesis of Core−Shell Ferrite Nanoparticles for Ferrofluids: Chemical and Magnetic Analysis

“…In such nanoparticles, several phenomena can occur: first, because of finite size effects, the magnetization of the nanograins, which are here all smaller than a Bloch wall, can be substantially increased by eventual cation redistributions; , second, finite-size and surface effects (such as the formation of a magnetically dead layer on the surface, the existence of random canting of surface spins, and nonsaturation effects due to imperfect orientation of the particle magnetic moment under the applied field) usually induce a reduction of the nanograin magnetization even observed at room temperature. , Here a redistribution of the divalent ions Zn 2+ is obvious in zinc ferrite nanoparticles ((nanoparticles) > m s (bulk)). It leads to a ferrimagnetic behavior which is consistent with EXAFS measurements and Rietveld refinement of XRD patterns performed with similar ZnFe 2 O 4 nanoparticles. , On the contrary, for NiFe 2 O 4 and CoFe 2 O 4 , we observe(nanoparticles) < m s (bulk): finite size effects are thus obvious in these two materials and cannot be excluded with the two other materials. For CoFe 2 O 4 particles a strong reduction of the magnetization saturation has been previously observed and attributed to finite size effects .…”

“…It leads to a ferrimagnetic behavior which is consistent with EXAFS measurements and Rietveld refinement of XRD patterns performed with similar ZnFe 2 O 4 nanoparticles. 27,28 On the contrary, for NiFe 2 O 4 and CoFe 2 O 4 , we observe m s p (nanoparticles) < m s (bulk): finite size effects are thus obvious in these two materials and cannot be excluded with the two other materials. For CoFe 2 O 4 particles a strong reduction of the magnetization saturation has been previously observed and attributed to finite size effects.…”

Rietveld structure refinement of the cation distribution in ferrite fine particles studied by X-ray powder diffraction

“…2 exhibits the experimental X-ray diffraction pattern for sample 2. Table 2 [11] for ZnFe 2 O 4 samples, prepared by the same method, with different diameters, using the Rietveld refinement of X-ray diffraction data. Indeed, the inversion degree found in sample 2 agrees with the values found from Mo¨ssbauer spectroscopy measurements in the presence of an external magnetic field parallel to the direction of the g-rays propagation, using CuFe 2 O 4 samples prepared by the same method, with different diameters [12].…”