Microwave refluxing was found to be a suitable method to produce single phase magnetic nanoparticles of Ni_xFe_3-x0₄. Ethylene glycol employed in the synthesis plays a crucial role in restricting the particle size to nano dimensions. X­my diffraction studies, Mossbauer spectroscopy and mag­netic measurements suggest that as-prepared samples were small in size (~15 nm) and hence dbl'lay low saturation magnetization values (44-60 emu g^-l). Ni_xFe_3-x0₄tnms­forms into γ-Ni_yFe₂__y0₃ and α-Ni_yFe₂__y0₃ after sintering at 720 and 1020 K resjiectively as mdicated by X-rdY diffmc­tion patterns. This was also confirmed by resistivity mea­surements. The electrical properties of the two tmnsformed phases were compamble to their bulk values. It has also been found that a large substitution of Ni stabilizes γ-phase at higher tempemture.