Magnetodielectric, electrical, and physicochemical evaluations of rare earth La3+doped spinel nano ferrites for microwave absorption applications

Electromagnetic (EM) pollution represents a significant challenge to human health, driven by the proliferation of high-frequency electromagnetic waves generated by electronic devices. Developing advanced materials with exceptional electromagnetic wave absorption, superior shielding capabilities, and efficient energy dissipation mechanisms remains a critical research frontier in materials science and electromagnetic interference management. Magnetic nanoparticles display exceptional and distinctive magnetic properties due to their elevated surface-to-volume ratio and diverse crystal structures. The characteristics of these nanoparticles are substantially affected by their synthesis method. Spinel ferrite made of Ni₀.₃Mn₀.₂Cd₀.₂₅Co₀.₂₅Fe2-xLa_xO₄ (x = 0.0, 0.01, 0.03, 0.05, 0.07) was prepared using the sol-gel auto-ignition method. X-ray diffraction (XRD) research provided comprehensive structural characterization, confirming the successful formation of the spinel crystal structure. The study demonstrated the formation of secondary crystalline phases upon the gradual increase in La concentration. This showed how the material's structure changed over time with dopant concentration. The crystallite size ranged from 48.28 to 58.07 nm. Advanced spectroscopic and analytical techniques such as FTIR, UV–Vis, XRD, and VSM were employed to evaluate the material's structural and physical properties. The FTIR analysis identified two significant bands between 572.76 and 598.75 cm⁻¹ and 443.97 and 462.38 cm⁻¹. These bands correspond to vibrations at the A and B sites, respectively. The optical band gap diminished from 3.41 eV to 2.96 eV with the augmentation of La³⁺ concentration. Dielectric experiments conducted with an LCR meter demonstrated frequency-dependent characteristics, wherein the dielectric constant, dielectric loss, and tangent loss were reduced, but AC conductivity increased with frequency. M_s diminished from 87.32 emu/g to 53.84 emu/g, Mᵣ declined from 38.41 emu/g to 4.68 emu/g, and Hc first fell from 737 Oe to 171 Oe, thereafter experiencing a minor increase to 226 Oe with more La³⁺ doping. The narrow hysteresis loops validated the materials' soft magnetic characteristics. The lowest reflection loss of −37.89 dB was achieved at 0.48 GHz for x = 0.03. At higher doping concentrations of x = 0.05 and x = 0.07, the reflection loss values are-28.25 dB and −28.17 dB, respectively. The La³⁺-substituted Ni–Mn–Cd–Co nanocrystalline ferrites have properties that can be changed, making them good choices for use in electronics, magnetic systems, and other microwave high-frequency applications.