Structural and magnetic properties of CoFe₂O₄ nanoferrite simultaneously and symmetrically substituted by Mg, Sr and Mn

Mg_xSr_xMn_xCo_1−3xFe₂O₄ nanoferrite series (with x = 0, 0.1, 0.2, 0.3, 1/3) were synthesized by glycol-thermal technique. The average crystallite size, lattice parameter, X-ray density and microstrain were calculated from X-ray diffraction data and the average crystallite size confirmed by high-resolution transmission electron microscopy in the range of 7.5–9 nm. Energy dispersive X-ray spectroscopy was used to identify qualitatively the constituent elements in the synthesized compounds. High resolution scanning microscopy scans show almost spherical shaped nanoparticles. Mössbauer spectroscopy measurements reveal magnetic order of the compounds at about 300 K and the distribution of Fe³⁺ ions at tetrahedral and octahedral sites. The sample at x = 1/3 has the lowest coercive fields, magnetizations and hyperfine fields. At low temperature magnetic measurements of the series shows spin freezing effects for samples x = 0, 0.1, 0.2 and significant changes in magnetizations and coercive field as a function of composition and temperature. - Highlights: • Mg_xSr_xMn_xCo_1−3xFe₂O₄ nanoferrites were produced by glycol-thermal method. • Samples become magnetically harder at lower temperatures due to spin freezing. • Correlation between coercive fields and the blocking temperatures are observed. • Coercivity and magnetization follow Kneller's and modified Bloch's laws respectively