Structural and magnetic characterization of Zr-substituted magnetite (Zr_xFe_3-xO₄, 0≤x≤1)

We report the preparation of monophasic Zr-substituted magnetite (Zr_xFe_3-xO₄; 0≤x≤1) nanoparticles by wet chemical route. Such a report is lacking in the literature. Rietveld refinement of the X-ray diffraction (XRD) data suggests continuous decrease in the lattice parameter with increased Zr-substitutions. From TEM analysis, the size of the as synthesized particles was found to be in the range of 5-20 nm. The differential scanning calorimetry (DSC) curves for the samples with different amount of substitutions displayed considerable differences in their behaviors. The room temperature specific magnetization at 2 T has been found to decrease from 50 (x=0.2) to 41 A m²/kg (x=1.0) with increased Zr-substitution. From XRD and magnetic behavior analysis we could suggest that due to occupation of Zr⁴⁺ ions at tetrahedral and octahedral voids of Fe₃O₄, the amount of Fe²⁺ was more at octahedral site for x≤ 0.4 and at tetrahedral site for x>0.4 respectively. The ferrofluids prepared from these magnetic nanoparticles possessed good heating ability and Specific Absorption Rate (SAR) values suitable for bioapplications.