Md Naimur Rahman, Md. Abul Hossain
Ferrite materials have attracted significant attention due to their tunable structural and magnetic properties, making them highly promising for modern technological applications. Transition metals play a crucial role in spinel ferrites, serving either as dopants or as primary divalent cations, and thus strongly influence their performance. Despite extensive studies, a systematic framework that links transition-metal incorporation to magnetic applications using modern synthesis methods and combined structural and magnetic property analysis is still limited. This review highlights several modern synthesis methodologies and emphasizes the relationship between structural and magnetic properties of transition-metal spinel ferrites, drawing insights from X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). Structural parameters, such as lattice constant, crystallite size, dislocation density, unit cell volume, and hopping length, provide insight into structural stability, bond geometry, and structural ordering. Similarly, magnetic parameters, including remanent and saturation magnetization, squareness ratio, coercivity, magnetic moment, and anisotropy, reflect domain stability, magnetic domain structure, and magnetic ordering. Reduced structural stability and altered bond geometry generally favor soft magnetic states (superparamagnetic, paramagnetic, diamagnetic, antiferromagnetic), whereas enhanced stability supports hard magnetic states (ferromagnetic, ferrimagnetic). Notably, transition-metal doping improves both structural and magnetic properties, broadening the potential of spinel ferrites for next-generation technological applications.