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.

Magnetic entropy change as a function of temperature for various Co _{1− x} Cr _x Fe ₂ O ₄ at an applied magnetic field of 5 T.

Structural, electronic, optical, and thermal properties of undoped and metal, M (Ni, Cu, and Zn), doped cadmium iodide (CdI₂) were studied using a generalized gradient approximation of density functional theory. Lattice constants found from the theoretical studies of the structure of the undoped and doped CdI₂ are in good agreement with those found in the available experimental and theoretical investigations. A strong mixing of I 5p and M 3d states is found after the doping of 3d M in CdI₂, which alters the bandgap from positive to negative. Among all M (Ni, Cu, and Zn), Ni doped CdI₂ with a narrow negative bandgap evolve the quantum dot level. Due to interactions between the Cd 4d and M 3d states, the measured optical and thermal properties of the doped system assessed with pure CdI₂ indicate unusual behaviors, which suggest that the material can be used in different nano-electronic and electrochemical applications and in biological levels such as detection of COVID-19 pathogens.

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.