Investigation of the structural, magnetic, and dielectric properties of Al-substituted Li-Ni-Mn ferrites

The standard solid-state reaction method is used to synthesize Aluminium (Al) substituted lithium-nickelmanganese ferrites. The synthesized samples were sintered at a temperature of 12000C for 5h. The confirmation of single-phase cubic spinel structure is revealed by Reitveld refinement analysis. The average grain size is determined to be within the range of 1.72 to 0.91 mu m based on the analysis of surface morphology. The densities showed a slight declination with Al contents because the Al3+ ion has less molecular weight than the Fe3+ ion and porosity increased gradually. The real part of initial permeability (mu i') is gradually decreased with Al substitution. The lowest value of magnetic loss (tan delta M) and the highest value of mu i' is obtained for the mother material (mu i'=68.5). The maximum value of relative quality factor (RQF) is found for x=0.20 sample and is approximately 1600. The sample of x=0.00 comprises the large value of saturation magnetization (=89.7 emu/g). Through the analysis of frequency-dependent dielectric constants and AC conductivity, it can be seen that the synthesized ferrites exhibit a high level of resistivity. The dielectric characteristics of the Al-substituted samples are improved, and the maximum dielectric constant (epsilon') of 3200 is observed for the x=0.40 sample at 102Hz. The Nyquist plot indicates that grain boundary contribution is significant to the conductivity mechanism of the compositions and that the materials exhibit non-Debye-type relaxation of conductivity. The studied samples showed ferroelectric properties with lossy behavior.