Structural, magnetic, and optical properties of Al 3+ ion-substituted Ni–Ba–Co ferrite prepared via sol–gel method

This work focuses on studying the structural, magnetic, and optical properties of Al 3+ ion-substituted Ni–Ba–Co ferrites with the composition formula Ni 0.2 Ba 0.1 Co 0.7 Fe 2-x Al x O 4 (0 ≦ x ≦ 0.4, step by 0.1). The samples have been prepared via sol–gel auto-combustion method. The prepared samples were analyzed by the X-ray diffraction. The lattice constant decreased with the Al 3+ ions substitution. Two obvious stretching vibrations bands about spinel ferrite were found in Fourier transform infrared spectroscopy. From SEM micrographs, it can be seen that the prepared particles are agglomerate and tightly distributed. Through Vibrating sample magnetometer, it revealed that an obvious correlation between magnetic properties and Al 3+ ions substituting contents. Ms decreased from 43.34 to 26.71 (emu/g) and Hc decreased from 872.66 to 456.15 (Oe). The decrease in Ms and Hc is due to Fe 3+ ions substituted by the Al 3+ ions. Through UV–Vis absorption spectrum analysis, the optical band gap energy ( E g ) of samples were in the range of 1.82–2.32 eV, and it revealed that the samples were of semiconductors.