Magnetic Order and Electronic Transport behaviour in Tailored made Nanostructural Co- Cr Ferrospinels

The unique size-dependent structural and physical properties of Cr³⁺-doped spinel ferrites, coupled with their wide range of applications, have garnered significant attention from the scientific community. In this work, CoCrₓFe₂₋ₓO₄ (x = 0.0, 0.5, 1.0, 1.5, and 2.0) compositions were synthesized using the citrate–gel auto-combustion method and subsequently sintered at 700°C for 6 hours. XRD analysis demonstrated that all samples crystallized in a pure cubic spinel phase. The lattice parameter was found to decrease slightly with increasing chromium content, ranging from 8.3862 Å to 8.3835 Å. The study of cation arrangement showed that Co²⁺ ions are chiefly positioned at octahedral (B) sites., while the relatively larger Cr³⁺ ions substitute for smaller Fe³⁺ ions at the same sites. FTIR spectra showed characteristic M-O stretching vibrations pertaining to the tetrahedral (A) and octahedral (B) lattice positions, further affirming the characteristic spinel phase. All dielectric parameters, such as dielectric constant, dielectric loss, and loss tangent, were found to decrease as the frequency increased. Magnetic characterization revealed that the replacement of Fe³⁺ by Cr³⁺ led to a decrease in saturation magnetization and an increase in coercivity, indicating the potential of these materials for permanent magnet applications.