Comparison of the effect of Cr3+ substituted Co-Cu and Cu-Co nano ferrites on structural, magnetic, DC electrical resistivity, and dielectric properties

Cr-3-substituted Co-Cu (Co0.7Cu0.3Fe2-xCrxO4) and Cu-Co (Cu0.7Co0.3Fe2-xCrxO4) nano ferrite composites were prepared using the sol-gel approach, where x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.25. We analysed their structural, DC electrical resistivity, magnetic, and dielectric properties comprehensively. X-ray diffraction (XRD) results indicate the formation of a single-phase spinel ferrite structure. The introduction of Cr3+ ions leads to a reduction in lattice volume and crystallite size. Field emission scanning electron microscopy (FESEM) images reveal non-spherical particles on a uniform surface, with a decrease in grain size as Cr3+ doping levels increase. The Fourier-transform infrared (FTIR) patterns are consistent with the XRD results, confirming the presence of spinel ferrite. The variation significantly influences the magnetic properties in Cr3+ doping. The saturation magnetization (Ms) decreases as the Cr3+ content increases to x = 0.1. Beyond that, it continues to decrease with higher Cr3+ concentrations. This behavior is attributed to the antiferromagnetic nature of Cr3+ ions, which do not favour their occupation at the B sites. The DC resistivity increases with higher Cr3+ concentrations and decreases with rising temperatures, indicating the semiconducting behavior of the ferrites. Furthermore, the loss tangent (tan delta) exhibits an exponential decrease with increasing frequency, pointing to typical Maxwell-Wagner-type dielectric dispersion driven by interfacial polarization.