Synthesis, characterization and magnetic properties of Cr-substituted Co–Zn ferrites nanopowders

Nano-crystalline ferrites; Co0.9Zn0.1Fe2−xCrxO4 (where x = 0–1) have been synthesized through thermal decomposition reaction of their respective oxalates. The effect of Cr3+ ion substitution on the structural and magnetic properties was studied. Differential thermal analysis-thermogravimetry (DTA–TG) techniques were used to characterize the oxalates decomposition reaction and following ferrite formation. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and vibrating scanning magnetometry (VSM) were used to characterize the structural, morphological and magnetic properties. XRD revealed single-phase cubic spinels. Both crystallite size and lattice parameter decreases with increasing Cr-content. FT-IR spectral studies confirmed the suggested cation distribution estimated through XRD measurements. TEM image showed agglomerated spherical nanoparticles with size of about 20 nm. The gradual decrease in the saturation magnetization, estimated through VSM measurements, with increasing Cr-content suggests the preferential occupation of Cr3+ ions in the octahedral sites and confirmed the suggested cation distribution while, the decrease in the coercivity values indicating the loss of magneto-crystalline anisotropy. The decrease in the Curie temperatures obtained from dc-magnetic susceptibility with the increasing chromium can be attributed to the decrease in the A–B exchange interaction.