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An easy method based on the chemical charge neutrality and low temperature magnetic measurements is proposed to estimate the cationic distribution of Co x Fe 3-x O 4 (0 3+ cations located in the octahedral B sites has been quantified and found to be increased with x (about 30% for x = 1.5). The results have been compared to the literature and found to be accurate with advance techniques as Neutron powder diffraction and in-field Mossbauer spectroscopy. The validity of our method is discussed: when the grain size is less than 6 nm and when the nanoparticles are in a core-shell structure the method cannot be applied. Furthermore, the dependence of the magnetocrystalline anisotropy on the cobalt content x is related to the evolution of the Co 3+ cations. Our method offers the possibility to calculate the cationic distribution of spinel ferrite systems ones they have the suitable physico-chemical properties.

International audience; In this work, we present a correlation between High Resolution Transmission Electron Microscopy (HRTEM) and in-field Mössbauer spectrometry to point out exchange coupling behavior, surface effects and chemical disorder in CoxFe3-xO4 cobalt ferrite nanoparticles. The samples were synthesized by a solvothermal chemical route. The hysteresis loops, recorded by using Vibrating Sample Magnetometer (VSM), suggest a jump-like behavior nearby zero applied magnetic fields. The HRTEM micrographs illustrate the presence of faceted nanoparticles for x

Cobalt ferrites nanoparticles Co x Fe 3-x O 4 (1≤ x B ) range from 294 to 240 K. Kneller's law fitting of the coercive field dependence on the temperature exhibits a non-neglected interparticle interaction and a wide size distribution according to the difference found between T B and the Kneller transition temperature T BK .

International audience; In this work, we report on magnetic nanoparticles of CoxFe3-XO4 (x 0) gives spinel structure of space group Fd-3m for all samples. Magnetization curves, recorded by a Vibrating Sample Magnetometer (VSM), are the sign of two exchange-coupled magnetic phases (x > 0). This was in disagreement with XRD and SAED analyses which showed only one structural phase. Large (similar to 250 nm and less) rectangular and small spheroidal nanoparticles have been found by Transmission Electron Microscopy (TEM). The increase of cobalt content favors the formation of monodisperse nanoparticles. Following a subsequent heat treatment, a fraction of the as prepared samples (depending on x) has been transformed into hematite phase with a disappearance of the exchange-coupling behavior. In situ Micro-Raman analyses were necessary to investigate on the growing of the nanoparticles and the ferrite-hematite transformation. We have also deduced, that the synthesized phase with the cobalt ferrite one (till x < 1) was the magnetite Fe3O4. Then, we have pointed out the effect of performing local spectroscopy and the effect of having mixed ferrites on the structural and the physical properties. (C) 2016 Elsevier B.V. All rights reserved.

In the present work, we have studied the effect of metal nanoparticles on the enhancement of the sensor response. These nanoparticles were deposited on the surface of WO3 sensors.