Influence of the Mn/Fe ratio on structural, optical, electrical and magnetic characteristics of MnFeMgNiO spinel ferrites.

[Display omitted] • Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 spinel ferrites were prepared utilizing a flash auto-combustion technique. • XRD confirmed formation of cubic phase spinel ferrite phase with space group Fd-3 m. • FTIR spectra validate the positions of the cations and their vibrational modes. • Optical band gaps Eg of investigated samples were found to decrease from 1.79 eV to1.24 eV. • The magnetic properties demonstrated soft ferrite nature with small hysteresis curve. Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 spinel ferrite nanoparticles (0.0 ≤ x ≤ 1) were prepared utilizing a flash auto-combustion technique. The as-prepared ferrite nanoparticles have been investigated and characterized using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared analysis (FTIR). The dielectric, optical and magnetic characteristics of the synthesized spinel ferrite samples were investigated using broadband dielectric spectroscopy (BDS), diffuse reflectance spectroscopy (DRS) and vibration sample magnetometers (VSM). The cubic phase spinel ferrite with space group Fd-3m was identified through XRD. X-ray diffraction indicates that the lattice constant increases and the crystallite size declines with increasing Mn concentration. The positions of the cations and their vibrational modes in the crystal structure with oxygen ions are demonstrated through the FTIR spectra. The morphology was examined using HRTEM showed polycrystalline cubic spinel structure with faceted planes. The optical band gap Eg was determined using Kubelka–Munk model where, it decreased from 1.79 eV to1.24 eV as Mn content increases. The replacement of manganese significantly affects the dielectric characteristics of the synthesized spinel ferrites. The real (ε′), imaginary (ε″) parts of dielectric constant and ac conductivity exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases. The presence of a relaxation phenomenon in all prepared samples except the undoped sample (Ni 0.5 Mg 0.5 Fe 2 O 4) is shown by the imaginary modulus's (M′′) dependence on frequency. The magnetic properties exhibited soft ferrite nature with small hysteresis curve for all spinel ferrites samples. The magnetic properties of Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 nanoparticles were measured and analysed, including saturation magnetization (Ms), remanence (Mr), coercivity (Hc), and squareness ratio. (Ms), and (Mr), exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases while squareness ratio decreased. The magnetic parameters greatly affected by Mn substitution ratio. [ABSTRACT FROM AUTHOR]