Effect of Zn concentration on crystal structure and magnetic properties of ZnxNi1−xFe2O4 nanoparticles fabricated by co-precipitation method

Zn
_x
Ni
_1-x
Fe
₂
O
₄
magnetic nanoparticles with various x from 0.2 to 0.8 have been synthesized by a chemical co-precipitation method. The X-ray diffraction (XRD) patterns confirmed that nanoparticles have spinel cubic structure with some impurity phases. The lattice parameter of the sample for x = 0.2 was 8.599 Å and then increases with the increase of Zn concentration. This is due to the replacement of smaller Ni
²⁺
by larger Zn
²⁺
cation. The crystallite size of the sample for x = 0.2 about 21.5 nm and then decrease by the increase in Zn content. It is due to the lower bond energy of Zn
²⁺
-O
^2-
(159 kJ/mol) as compared with Ni
²⁺
-O
^2-
(451 kJ/mol). The Fourier transform-infrared (FT-IR) spectra between 400 and 4000 cm
^-1
confirmed the intrinsic cation vibrations of the spinel structure. Transmission electron microscopy (TEM) pattern showed that the sample seem to be agglomeration with spherical shape. Vibrating sample magnetometer (VSM) measurement showed that the values of the maximum magnetization at 15 kOe increased from 5.9 to 18.5 emu/g by decreasing of Zn content. The coercivity (Hc) values of of the sample for x = 0.2 was 48.4 Oe and then decreases with the increasing of Zn content. It is due to the decrease in the magnetocrystalline anisotropy attributed to the absence of Ni
²⁺
cation.