Magnetic and electric properties of nanoparticles of Ni-substituted ferrites synthesized using a microwave refluxing process

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Microwave refluxing was found to be a suitable method to produce single phase magnetic nanoparticles of Ni x Fe 3− x O 4 . Ethylene glycol employed in the synthesis plays a crucial role in restricting the particle size to nano dimensions. X-ray diffraction studies, Mössbauer spectroscopy and magnetic measurements suggest that as-prepared samples were small in size (∼15 nm) and hence display low saturation magnetization values (44–60 emu g −1 ). Ni x Fe 3− x O 4 transforms into γ-Ni y Fe 2− y O 3 and α-Ni y Fe 2− y O 3 after sintering at 720 and 1020 K respectively as indicated by X-ray diffraction patterns. This was also confirmed by resistivity measurements. The electrical properties of the two transformed phases were comparable to their bulk values. It has also been found that a large substitution of Ni stabilizes γ-phase at higher temperature.