Synthesis, Characterization and Superparamagnetic Resonance Studies of ZnFe₂O₄ Nanoparticles

Abstract

Superparamagnetic nanoparticles of zinc ferrite (ZnFe2O4) were produced by a microwave induced combustion synthesis method. XRD, FT-IR, SEM, VSM and ESR were used for the structural, morphological, and magnetic investigation of the product, respectively. Average particle size of the nanoparticles was estimated by the Schérrer equation using the full-width at half maximum (FWHM) of the most intense XRD peak and found as 41 nm. Magnetization measurements have shown that the samples have a blocking temperature of 72 K which indicates a superparamagnetic behavior. Superparamagnetic resonance (SPR) spectra at room temperature show a broad line with a Landé g-factor, g(eff) approximately 2. We used a theoretical formalism based on a distribution of diameters of the nanoparticles following lognormal proposed by Berger et al. The nanoparticles behave as single magnetic domains with random orientations of magnetic moments which are subject to thermal fluctuations. A Landau-Lifshitz line shape function presents adequate results which are in good agreement with the experimental ones. At high temperatures, the SPR line shape is governed by the core anisotropy and the thermal fluctuations. By decreasing the temperature, the magnetic susceptibility of shell spins increases. As a result of this, the surface spins produce an effective field on the core leading to a decrease of resonance field, B(r). Also, the effective anisotropy increases as the shell spins begin to order. So, the results are interpreted by a simple model, in which each single-domain nanoparticle is considered as a core-shell system, with magneto-crystalline anisotropy on the core and surface anisotropy on the shell.

Minute-Made, High-Efficiency Nanostructured Bi2Te3 via High-Throughput Green Solution Chemical Synthesis

“…MW speeds up the chemical reaction by increasing the overall kinetics of the reaction as it relies on localized superheating [ 71 ]. Other advantages of using MW heating are higher yields, and since the reaction is kinetically driven it ensures a narrow-size distribution of the particles [ 72 ]. A variety of nanomaterials have been synthesized with MWs, including 0D [ 63 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ], 1D [ 67 , 68 , 79 , 80 ] and 2D structures [ 81 ].…”

“…Other advantages of using MW heating are higher yields, and since the reaction is kinetically driven it ensures a narrow-size distribution of the particles [ 72 ]. A variety of nanomaterials have been synthesized with MWs, including 0D [ 63 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ], 1D [ 67 , 68 , 79 , 80 ] and 2D structures [ 81 ]. MW-assisted synthesis is also a sustainable, environmentally friendly, and economically viable heating method for bulk commercial scale production of strategic nanomaterials.…”

Magnetic studies of 0.7(Fe2O3)/0.3(ZnO) nanocomposites in nanopowder form and dispersed in polymer matrix

“…Magnetic properties of ZnFe 2 O 4 nanoparticles have been the subject of many studies because they are interesting and different than the ones registered in other ferrite spinels [7][8][9][10][11][12]. Bulk ZnFe 2 O 4 Magnetic studies of 0.7(Fe 2 O 3 )/0.3(ZnO) nanocomposites.…”

Effect of Excess Iron on Oxidative Dehydrogenation of 1-Butene over a Series of Zinc Ferrite Catalysts

“…This structure is ferrimagnetic because the octahedral and tetrahedral sub lattices are anti parallel and with twice as many octahedral sites than tetrahedral ones, the magnetic moment is uncompensated. It has previously been determined that stoichiometric zinc ferrite displays a short range anti ferromagnetic ordering at higher temperatures, which gives rise to the super paramagnetism at room temperature [43,44]. The prepared zinc ferrites are also super paramagnetic; hence it was necessary to dilute the samples in ZnO in order to carry out the EPR measurements in the 0.34T magnetic fields.…”