| Description |
This work demonstrates the versatility of the reverse micelle technique as a reaction control system for producing nanoparticles. A significant portion of this research involved elucidation of the effect of altering the reaction parameters on subsequent the nanoparticle product. The benefits of having developed a good understanding of the reverse micelle reaction parameters can be seen in the ease at which the process was adapted to the nickel-zinc ferrite nanoparticles and indium doped nickel-zinc ferrite nanoparticles. The simultaneous application of Mössbauer spectroscopy and magnetic investigation appears a powerful tool to investigate the structure, spin dynamics and magnetic properties of nanoparticles. The comparative in-field Mössbauer study of the bulk and nanosized particles enables us to separate the surface effects from the bulk effects in nanoparticles. As a consequence of spin canting and site exchange of cations in the surface shell, ferrite nanoparticles exhibit a reduced nonsaturating magnetization compared to bulk particles. The thickness of the surface shell estimated from Mössbauer measurement is found to be in agreement with that obtained from magnetization measurements. Finite size effects have implications on the temperature dependence of the saturation magnetization. The fit of the saturation magnetization to the Bloch T3/2 law for nanoparticles yields a Bloch constant larger than the bulk particles. The larger value of Bloch constant (b) suggests the possibility of interactions among the nanoparticles.
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