Temperature dependent structural, morphological, FTIR, optical, magnetic properties of NiMgZn ferrites

NiMgZn ferrites with chemical composition Ni$_{0.2}$Mg$_{0.3}$Zn$_{0.5}$Fe$_{2}$O$_{4}$ nanomaterials were synthesized using the sol-gel technique. The various properties of the samples prepared at three different calcination temperatures (T) of 400, 450 and 500 $^{\circ}$C/5 hr were studied. The X-ray diffraction study confirmed the single-phase cubic spinel structure (JCPDS 08-0234) for 400 & 500 $^{\circ}$C calcined samples and with Fe$_{2}$O$_{3}$ as an impurity phase for 450$^{\circ}$C calcined sample with lattice parameter values 8.296 to 8.376 A$^{\circ}$. The surface morphology and EDX spectra observed with field emission scanning electron microscope (FESEM) images confirmed the nano-sized irregular shaped grain development at low calcination temperatures. The force constants are determined using FTIR spectroscopy confirmed the M-O bonds present in ferrites. Optical band gap properties studied and found that NiMgZn ferrites have band gaps in semiconducting region from 1.68 to 1.75 eV. The susceptibility-temperature ($\chi$-T) dependence is studied using a Bartington MS2B Dual Frequency instrument in heating and cooling modes and magnetic transition temperature (T$_{c}$) were determined. The highest magnetic susceptibility of 1293 is observed for 500$^{\circ}$C calcined material. By using VSM, the M-H loop, magnetic properties are studied, which showed that this material is ferrimagnetic. Also, the magnetic moments and saturation magnetizations (M$_{s}$) are calculated. The maximum saturation magnetization 97.20 emu/g is observed for 400$^{\circ}$C calcined sample.