Impact of the Sc³⁺/In³⁺ co-substitution on the structural, magnetic, and microwave characteristics of Co_0.5Ni_0.5Fe₂O₄ nanospinel ferrites

In this article, In³⁺ and Sc³⁺ ions dual-substituted NiCo nanospinel ferrites (ScIn→CoNiFe₂O₄ NSFs) have been synthesized through citrate-gel auto combustion method to investigate the effect of In³⁺ and Sc³⁺ ions on magnetic, and microwave characteristics. The following techniques TEM, SEM, EDX, and XRD were applied to characterize surface morphology, chemical composition, phase identification, and crystallinity of products, respectively. The XRD verified a phase formation of spinel structure with a minor amount of Sc₂O₃ was observed for products having x ≥ 0.04. The average crystal size (D_XRD) of the products was estimated within the 33–68 nm range using the Scherrer equation. SEM and HR-TEM analyses exhibited accumulating sphere-shaped particles. By fitting the room-temperature spectra obtained from Mössbauer spectroscopy (Moss), Hyperfine interactions were determined. The cation distribution shows that there is a migration of In³⁺ ions in the lattice in an A→B direction with increasing concentrations while the B site is preferred by the larger Sc⁺³. M−H plots for 300 and 10 K illustrated all products carried out with a ferrimagnetic character. An enhancement in saturation magnetization (M_s) was remarked with Sc–In doping ratio up to 0.04 and thereafter a drop as the Sc–In concentration increased. The tendency in M_s values might be described by correlating it to the cation distribution amongst O_h and T_d (octahedral and tetrahedral, respectively) sublattices. Temperature-dependent magnetization measurements were also investigated, which further confirmed the maintenance of the ferrimagnetic character throughout the temperature range 10–300 K. The peculiarities of the microwave properties have been analyzed by the measured S-parameters in the range of 6–18 GHz. It was assumed that the energy losses due to reflection are a combination of electrical and magnetic losses due to polarization processes and magnetization reversal processes in the region of inter-resonant processes. The average value of the reflection coefficient is −14.48 … −14.24 dB. A significant attenuation of the reflected wave energy opens up broad prospects for practical applications as coatings for providing electromagnetic compatibility.