Fabrication of Nd–Ho Cosubstituted Co_0.5Ni_0.5Fe₂O₄ Nanospinel Ferrites and Exploration of Their Microstructure, Magnetic, and Electromagnetic Characteristics

The composition and hyperfine structures of Nd³⁺-Ho³⁺ ions cosubstituted CoNi nanospinel ferrites (Co_0.5Ni_0.5Nd_<i>x</i>Ho_<i>x</i>Fe_2-2<i>x</i>O₄ (<i>x</i> ≤ 0.05) NSFs) as well as their magnetic and electrodynamic behavior have been presented. The compound Nd-Ho → CoNiFe₂O₄ (<i>x</i> ≤ 0.05) NSFs were produced using the sol-gel method. XRD powder patterns indicated phase- and substituent-induced modifications of crystallites. The SEM analysis indicated the homogeneous distribution of grains with Nd-Ho cosubstitution. It was found that the values of <i>x</i> had an impact on the hyperfine magnetic field of the A and B sites. The cation distribution was determined by using Mössbauer spectroscopy. The M-H loops' investigations showed that the current NSFs behave ferrimagnetically at both room and low temperatures. An almost continuous rise in the strength of the coercive field was noticed with a rise in Ho-Nd content. The value of calculated squareness ratio values was above 0.5 at both temperatures, entailing that the studied NSFs' structure is made of single magnetic domains. The electromagnetic characteristics of the samples can be explained by the main contribution to electromagnetic absorption being the electric energy losses. Electromagnetic absorbed materials can be applied to provide electromagnetic compatibility and develop functional electromagnetic shields.