Crystallite size induced crossover from paramagnetism to superparamagnetism in zinc ferrite nanoparticles

Influence of Precipitating Agent Concentration on Nanoparticles Size and Magnetic Properties of Zinc Ferrites

“…The spectra for samples annealed at 500 o C of CMC capped zinc ferrite nanoparticles prepared at different concentration of NaOH solution present strong peaks around 580 cm -1 corresponding to stretching vibrations of Me-O characteristic cubic spinel structure [11,49]. The two distinct vibrations presented in the spectra at 1382 cm -1 and 1638 cm -1 are attributed to symmetric and asymmetric vibrations of carboxylic group (COO-).…”

“…In bulk ZnFe2O4 has a normal spinel structure, in which all Zn 2+ ions occupy tetrahedral positions (A-sites) and all Fe 3+ ions octahedral positions (B-sites) being paramagnetic at room temperature, the transition to a magnetically ordered state occurs only at temperatures of about 10 K [11]. Magnetic properties of spinel ferrite nanoparticles are different from those of bulk materials and substantially depend on the particle size [12], [13].…”

“…a part of zinc ions occupy the sites B, and part of iron ions the sites A [14] and the spinel structure become a mixed one and as consequence to the apparition of spontaneous magnetization [15]. Among the various preparation methods developed to produce Zn ferrite nanoparticles, such as reverse micelle [16], sol-gel [17], hydrothermal [11], the coprecipitation is the most used. A big part of literature reports the synthesis of ferrites from nitrate precursors [11,[18][19][20][21][22][23][24][25][26][27][28][29] but special attention is recently given to metallic chlorides precursors [30]- [40] due to the higher solubility in water of the resulted sodium chloride compared to the sodium nitrite [32,33,37,38].…”