Impact of the indium content on structural, magnetic, and electrodynamic properties of nanocomposites based on In-substituted Sr hexaferrite and Ni–Zn spinel ferrite with excellent absorption characteristics

SrInxFe_12-xO₄/Ni_0.5Zn_0.5Fe₂O₄ (0.00 ≤ x ≤ 0.04) nanocomposites (SIFO/NZFO NCs) were synthesized using a one-pot sol-gel auto-combustion technique. The EDX method was used to verify the chemical composition. An X-ray diffractometer (XRD) was used for the structural analysis. Scanning electron microscopy (SEM) was used to study the morphological characteristics. The impact of indium doping on the magnetic properties of the nanocomposites was investigated using magnetization measurements at T = 300. A kink was observed in the M − H curves for lower indium content (x ≤ 0.02), which was suppressed with further increasing indium content until it vanished at a higher content. A single peak at a higher indium content replaced two peaks at a lower indium content (x 0.02), according to the switching field distribution (i.e., dM/dH vs. H). When the indium concentration increased, the saturation, remanence magnetization, and coercive field increased until x = 0.01, and then decreased, according to the analysis of the M − H loops. The obtained results reveal that an exchange interaction at the surface of the SIFO and NZFO nanoparticles (NPs) exists. The degree of intergranular dipolar interactions diminishes with increasing indium content within the hard-soft ferrite SIFO/NZFO NCs and becomes insignificant at higher indium contents. Moreover, the core of the SIFO and NZFO NPs also contains magnetic super-exchange interactions between Fe and O ions. At high frequencies (2–20 GHz), a correlation was found between the hard phase composition (indium content) and electrodynamic characteristics. Analyses were performed on the evolution of essential parameters (real and imaginary permittivity and permeability) in relation to the frequency. In this frequency range, the effect of electromagnetic radiation absorption was observed. A significant level of electromagnetic absorption (>-12 dB) in the frequency range was observed for investigated nanocomposites (NCs). The NCs with lower indium content (0.00 ≤ x ≤ 0.01) have higher reflection looses coefficients (−18 … -36 dB). This opens broad perspectives for the practical application of magnetic media for intensive electromagnetic absorption.