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Developing economically soft magnetic materials for high-performance electrical devices is indispensable. Here, we present the structural and magnetic properties of thermally reduced soft CuFe nanoparticles. The fcc cubic structure of iron-rich Cu37Fe63 and their composition was confirmed by Rietveld refinement. Cu37Fe63 nanoparticles exhibited high saturation magnetization and coercivity of 127 emu/g (142 emu/g) and 4.3 Oe (31 Oe), respectively, at 300 K (5 K). They showed transitions at $\sim 34$ and $\sim 249$ K due to the Kondo temperature of CuFe and minor fraction of CuFe2O4, respectively. The exchange coupling between Cu and Fe was not significant, as demonstrated by field-cooled magnetization curves at 5 K. The magnetocaloric effect (MCE) in the range of fields and temperatures was estimated whereas the maximum MCE of $-8.71\times 10^{-2}$ J.kg−1. $\text{K}^{-1}$ was achieved at 222 K. These soft magnetic materials, which exhibited stable high saturation magnetization with less heating effect during magnetization and demagnetization cycles, would be suitable candidates for magnetic applications. [ABSTRACT FROM AUTHOR]

Microwave-assisted co-precipitation method was adopted to analyze the effect of polyethylene glycol (PEG) and urea concentrations on the properties of cobalt ferrite nanoparticles (NPs). The average crystallite size of single phase cubic spinel cobalt ferrite NPs was controlled within 10-14 nm with the effect of PEG, urea and the combination of them. The transmission electron micrographs revealed that the morphology of cobalt ferrites was not significantly influenced by the different concentration of capping agents but almost uniform morphology with nearly narrow size distribution was obtained. The interaction of PEG and urea molecules on the surface of nanoparticles was mediated through -OH hydroxyl group affected the crystal growth rate. The possible interaction mechanism was proposed with the help of IR vibrational spectra. All the samples exhibited ferromagnetism at room temperature and it was found that the capping agents showed an effect on the magnetic properties. The maximum saturation magnetization of 58 emu/g was achieved when the urea of 60 mg was used and the maximum coercivity of 311 Oe was attained when the mixture of PEG (40 mg) and urea (20 mg) were used. Ultrafine and hydrophilic cobalt ferrite NPs that showed appreciable magnetic properties obtained in the present experimental procedure would be of great interest in various biomedical applications. [ABSTRACT FROM AUTHOR]

Cobalt ferrite (CoFe 2 O 4 ) nanoparticles were co-precipitated from metal nitrates at the reaction temperatures of 40 and 85 °C for 1 h and were further calcinated at 500 and 800 °C for 2 h. The effect of calcination temperature on the structural, morphological, compositional and magnetic properties was investigated. Both, the reaction and calcination temperatures were significantly influenced the crystallite size and magnetic properties of cobalt ferrite nanoparticles and the crystallite size was increased with the calcination temperature. The synthesized nanoferrites were roughly in spherical morphology with the stoichiometric ratio of 1:2 Co:Fe. Co-precipitated and calcinated cobalt ferrites showed the ferromagnetism at room temperature and 5 K (−268 °C) and the saturation magnetization was increased with the calcination temperature. At low temperature, CoFe 2 O 4 nanoparticles calcinated at 800 °C showed the saturation magnetization of 84.36 and 92.70 emu/g for the reaction temperatures of 40 and 85 °C, respectively and the values were in accordance with the magnetization of bulk cobalt ferrites. [ABSTRACT FROM AUTHOR]

Abstract: A combustion route of synthesizing highly crystalline single phase nickel ferrite (NiFe2O4) spinel nanoparticles using various amounts of dl-alanine as fuel has been reported in this paper. The role of the amount of fuel is found to be significant in the size control and phase purity of nano crystalline samples. The structural, thermal, morphological and magnetic studies have been carried out. XRD patterns reveal the formation of highly crystalline nano NiFe2O4 with high degree of phase purity when fuel concentration is maintained at 1M and 2M. FTIR spectra also prove the formation of pure nano NiFe2O4. The temperature and fuel effects are found to have strong influence on size, structural, and magnetic properties of materials. The magnetic measurements show that the nano NiFe2O4 samples exhibit soft ferromagnetism with the highest saturation magnetization Ms at room temperature as 42.53emu/g. [Copyright &y& Elsevier]