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In this research, NiFe 2 O 4 -based composite nanopowder with 0.8, 1, 1.35, 1.7 fuel-to-oxidant (F/O) ratios was synthesized by sol-gel auto-combustion method. Changes in phase constituents, microstructure and magnetic properties due to changes in F/O ratios were evaluated by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) techniques. XRD and Raman spectroscopy results show the presence of NiFe 2 O 4 , FeNi 3 , a-Fe 2 O 3 and NiO phases. The amount of nickel ferrite was increased, while the amount of FeNi 3 was decreased with increasing F/O ratio from 0.8 to 1.35. Mean crystallite sizes of the samples are in the range of 40-46 nm. FESEM studies depicted the formation of NiFe 2 O 4 particles coexisting with FeNi 3 phase. Changes in F/O ratios alter the saturation magnetization values from 37 to 60 emu/g as a result of changes in FeNi 3 and NiFe 2 O 4 amounts. Coercivity values are in the range of 135-177Oe. Graphical Abstract In this research nano-sized NiFe 2 O 4 powders with 0.8, 1, 1.35, 1.7 Fuel to Oxidant (F/O) ratios were synthesized by sol-gel auto-combustion method. FESEM studies depicted the formation of NiFe 2 O 4 particles coexisting with FeNi 3 phase. Changes in F/O ratios alter the saturation magnetization values from 37 to 60emu/g as a result of changes in FeNi 3 and NiFe 2 O 4 amounts. Coercivity values are in the range of 135 to 177Oe.

In this research, nickel ferrite nanoparticles were synthesized by sol-gel auto-combustion route, and the effect of calcination temperature on phase constituents, magnetic properties and microstructure of the synthesized nanoparticles was evaluated using X-ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and Scanning Electron Microscopy (SEM). XRD results were submitted to quantitative analysis. Microstructural studies and crystallite size calculations showed formation of nanoparticles. XRD results showed that the combustion product consisted of NiFe2O4, α-Fe2O3, NiO, and FeNi3 phases. FeNi3 was eliminated by calcination, and the amounts of NiO and α-Fe2O3 were modvlated by changing in calcination temperature. Saturation magnetization changed from 37emu/g in combustion product to 30emu/g by calcination at 600°C, due to decomposition of FeNi3 magnetic phase and formation of higher amount of antiferromagnetic hematite phase. Also, the