Magnetic properties of nanosize NiFe2O4 particles synthesized by sol–gel auto combustion method

Synthesis of a NiFe2O4 catalyst for the preferential oxidation of carbon monoxide (PROX)

“…The average crystallite size, crystallinity, lattice parameter, and microdeformation were 29 nm, 73.4%, 8.332 Å and 0.003612, respectively. Comparing the result of crystallite size (29 nm) obtained in this work with the result reported by Azadmanjiri et al [7] for this same system prepared by sol-gel method that was 72 nm, high efficiency of the combustion synthesis in the preparation of nanosized powders can be observed. With regard to the lattice parameter it can be verified that significant variation between theoretical value (8.339 Å) and experimental ones (8.332 Å) was not presented.…”

Novel preparation and properties of magnesioferrite nanoparticles

“…Investigation of this table reveals that: (i) The increase in the G/N ratio up to 2 led to an increase in the values of M s , M r and M r /M s depending upon the significant increase in the crystallite size [39]. The sample M5, which has a higher crystallite size (66 nm), On the other hand, the decrease in the value of M s due to the decrease in the G/N ratio could be attributed to smaller particle sizes [42].…”

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

“…Values of saturation magnetization are rather lower to the value corresponding to bulk ferrite (56 emu/g) pointing to some degree of non collinear spin structure usually explained with a core-shell particle model [10]. Regarding coercive field, it is clear that over 800 ºC it diminishes strongly Figures expressed in Table 1 are in the same order of magnitude that analog spinel ferrite nanoparticles or Ni ferrite synthetized with other methods [11][12][13][14] Finally, the sample with the lower annealing temperature studied (400 ºC) exhibits a qualitatively different hysteresis loop, with non attainment of saturation, that can be understood as the onset of superparamagnetic behaviour [10], in which the best model is a core shell morphology with a ferrimagnetic core and a surface layer on the shell with broken superexchange bonds between magnetic cations that induce a large surface spin disorder, so that , any increase in the applied field has an effect only on the surface layer of the particles. Since this layer does not have a very high response to the applied field, the overall increase in the magnetization of the particles slows down, and hence a high field magnetization irreversibility occurs.!…”

“…The figures calculated for anisotropy fields lie in the range of 0,8 to 1.7 KOe. This values are in the same order of magnitude that analog spinel ferrite or Ni ferrite nanoparticles synthetized with other methods [11][12][13][14], and roughly follow the evolution observed with the saturation magnetization so, unless there are other parameters which we do not have accounted for, like shape anisotropy that can also change in the series analyzed due to some degree of non-spherical shape or different degree of particle agglomeration, we can assume that crystalline anisotropy do not change abruptly with annealing temperature. Anyway, further research to elucidate some of the above mentioned hypotheses has to be carried out.…”