Pechini citrate-gel synthesised In3+ substituted X-type barium zinc hexaferrites: An investigation on structural, optical, magnetic and dielectric properties

Indium substituted X-type Ba2Zn2InxFe28-xO46 (0.0≤x≤2.0) ferrites were synthesised by a citrate-gel aqueous combustion technique, and heated at 1300 °C. XRD, FTIR, SEM with EDX, magnetic hysteresis, Mössbauer spectroscopy, UV–visible spectroscopy, and dielectric measurements up to 20 GHz have been carried out to study the modification of the structural, morphological, magnetic, optical and frequency dependant dielectric properties when indium is introduced, replacing iron in the lattice of X-type hexaferrites. XRD analysis reveals formation of a major X-type phase in all compositions. The systematic rise in lattice constants (a, c) along with cell volume (V) confirm the replacement of iron by indium. Magnetic hysteresis loops reveal a soft ferrite nature with low Mr/MS values, suggesting a multidomain structure in all samples. The HC values decrease from 22.22 kA m-1 to 12.18 kA m−1 (279 Oe to 153 Oe) with increasing indium, while magnetisation remained high between 56 A m2 /kg and 62 A m2/kg for all samples. Room temperature Mӧssbauer spectra of all samples were fitted with six Zeeman sextets of five different magnetic sublattices. It was ascertained that In-substitution reduces the Fe population in the k (spin up) sublattice, resulting in a reduction in magnetisation. The average hyperfine magnetic field is also reported to decrease with Indium substitution for all samples. The value of the isomer shift (δ) confirmed that the iron-ions are in high spin Fe3+ state. The complex impedance and electric modulus plots reveal non-Debye type relaxation in all samples at 100 Hz to 2 MHz.