Structural, elastic and cation distribution properties have been investigated on stoichiometric and non-stoichiometric cobalt ferrites. Crystal structure, formation of spinel type ferrite, chemical bonding, cation distribution, and thermal properties of two series of Cr³⁺ substituted stoichiometric and non-stoichiometric various cobalt ferrites with general formula Co_1−xCr_xFe₂O₄ (S1), and Co_1+xCr_xFe_2−xO₄ (S2) were reported. Samples are synthesized by the solid-state reaction technique via planetary ball milling. X-ray diffraction (XRD) analysis confirms the formation of a single phase cubic spinel structure with the space group Fdm. Rietveld refinement results show that Cr occupies both the tetrahedral (A-site) and octahedral sites (B-site). The experimental lattice parameters show increasing trends for both the series with increase of Cr content. The cation–anion vacancies, chemical bonding, and the displacement of oxygen have been evaluated to understand the effect of Cr substitution and how the non-stoichiometry affects the physical and chemical properties of the material. The crystallite size is found to be the decreasing value with an increase of Cr concentration for both series of samples. Specific vibrational modes from the FTIR spectra suggest a gradual change of inversion of the ferrite lattice with the increase of Cr concentration which is also evident from Rietveld refinement data. The elastic properties analysis reveals that the synthesized samples for both series are ductile in nature. The non-stoichiometric structure with excess Co²⁺ may pave a new way to realize the lowering of Curie temperature of ferrite that is expected to improve the magnetocaloric properties.

This paper reports on the structural and magnetic properties of a ball-milled powder sample of (Fe_1−xMn_x)₇₅P₁₅C₁₀ (x = 0, 0.05, 0.1, 0.2, and 0.3) mixed metallic amorphous ribbons. X-ray diffraction patterns of the as-made powder samples demonstrate a structural phase transition from amorphous to the nanocrystalline structure having a tetragonal (P) type structure. Field emission scanning electron microscopic micrographs show that the particles form a nanocrystalline structure presumably due to the stress relaxation upon ball milling the amorphous ribbons. The observed phase transformation and the changed magnetic properties, e.g., significant enhancement in the coercive field leading to magnetic hardness, are attributed to the controlled milling and Mn substitution in this mixed metallic alloy system, which is the novelty of this research work.