Effect of Cetyl trimethylammonium bromide (CTAB) amount on phase constituents and magnetic properties of nano-sized NiFe2O4 powders synthesized by sol–gel auto-combustion method

• NiFe2O4 was synthesized by sol–gel auto combustion with different CTAB contents.
• CTAB addition affects phase constituents and refines the microstructure.
• By 3 wt.% of CTAB addition Mmax of the synthesized powder reached to 51 emu/g.

In this research nano-sized NiFe2O4 powders were synthesized with and without Cetyl trimethylammonium bromide (CTAB) surfactant addition by sol–gel auto-combustion method. Phase constituents, microstructure and magnetic properties as a result of different CTAB addition amounts were evaluated by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM) and vibration sample magnetometer (VSM) techniques. XRD results designated that the combustion product consists of NiFe2O4 as the main phase and some amount of α-Fe2O3 and FeNi3 phases. Raman spectroscopy represents the formation of NiO phase in addition to the mentioned phases. CTAB addition affects the phase constituents and elimination of α-Fe2O3 residuals from the combustion product while facilitating the formation of FeNi3 phase. Also its addition leads to powder refinement based on FESEM images. Mean crystallite sizes of the samples by calculated by Scherrer equation showed a decreasing trend from 46 to 27 nm with increasing the amount of CTAB. Magnetic measurements showed that saturation magnetization increased from 36.96 emu/g to 51.07 emu/g by CTAB addition as a result of increased FeNi3 amount. The intrinsic coercivity values (iHc) of the samples are in the range of 164–175 Oe.