Dependence of structural and magnetic properties of CoFe2O4/SiO2 nanocomposites on annealing temperature and component ratio

Investigations on structural and magnetic properties of cobalt ferrite/silica nanocomposites prepared by the coprecipitation method

“…These results correspond to the production of well crystallized cobalt ferrite. It is worth mentioning that a similar phase was developed at higher temperatures (600-1000 1C) as reported by other workers [38][39][40][41][42]. Moreover, at 300 1C (2 h), the elimination of water molecules, Si-OH and volatiles in the samples occurred resulting in the densification of CoFe 2 O 4 /SiO 2 , which is confirmed by XRD.…”

“…The magnetic parameters of different samples are listed in Table 1. It is found that the values of saturation magnetization (M s ), remanent magnetization (M r ) and coercivity (H c ), which were measured at room temperature (300 K), first increases with increase in annealing temperature which can be attributed to the influence of the average particle size induced by 20 nm Direct Mag: 600000x the annealing temperature [43] and then decreases with further increase in annealing temperature, which may be due to: (i) grain boundaries interaction and interfaces, as the length of interactions can span many grains and is critically dependent on the character of interface and (ii) strain produced in cobalt ferrite crystallite because of the difference in thermal coefficient of CoFe 2 O 4 and SiO 2 [44]. Interestingly, it is observed that the values of M s , M r and H c increase with decrease in measuring temperature because the magnetization direction of nanoparticles is frozen to the direction of applied field and the anisotropy barrier prevents the magnetization direction of each nanoparticle from flipping, which is in agreement with the results described elsewhere [45].…”

“…Peaks in diffractograms were indexed by comparing the interplanar distances with JCPDS data. The powder sample calcined at 100 1C for 2 h, shows diffraction peaks at 2y $30.081 (2 2 0), 35.411 (3 1 1), 43.081 (4 0 0), 56.961 (5 1 1) and 62.51 (4 4 0). These diffraction peaks may be assigned to spinel face centered cubic cobalt ferrite (JCPDS File No.…”

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

“…No diffraction peaks of impurities were observed in the patterns. It showed that in comparison with the previous report using TEOS as a silica precursor [37], Co-ferrites with more crystallinity have been successfully synthesized at lower calcination temperatures under current mild experimental conditions.…”

Investigations of lanthanum doping on magnetic properties of nano cobalt ferrites

“…However, H C does not follow the variation of M S and M R . Its variation depends upon a number of factors like microstructure, particle/grain size, residual strain and many other complex factors [17][18][19].…”