Correlations between microstructural and magnetic properties of Gd3+-doped spinel ferrite nanoparticles

We report the effect of rare-earth Gd3+ doping in Ni–Zn ferrite nanoparticles with a generic formula Zn0.2Ni0.8GdxFe2–xO4 (x = 0.00, 0.05, 0.10 and 0.15), synthesized using chemical co-precipitation technique. The cubic spinel phase formation and phase purity were confirmed using X-ray diffraction with crystallite size in the range of 16 ± 7 nm obtained from Scherrer’s formula and Williamson–Hall (W–H) plots analysis. The lowering of octahedral cubic symmetry was also observed from Raman spectra with increasing Gd3+ ions content. Increase in Gd3+ ions concentration results in enhancement of A–O–B superexchange magnetic interaction, confirmed by hysteresis curves at 5 K. The room temperature M–H plots showed superparamagnetic behavior due to small particle size. The blocking temperature was found to decrease with increase in Gd3+ ions concentration in Ni–Zn ferrite nanoparticles, which makes it a potential candidate for biomedical applications such as targeted drug delivery and hyperthermia.