Dysprosium doping induced shape and magnetic anisotropy of Fe3−xDyxO4 (x=0.01–0.1) nanoparticles

• Report on formation of nanorods in magnetite prompted by Dy doping.
• Observation of anisotropic magnetic behaviour emanating from the shape anisotropy.
• Evidence of Dy3+ ions occupying octahedral site in place of Fe3+ ions.
• Nanorods envisaged to be useful as catalysts and in biomedical applications.

The effect of dysprosium doping on evolution of structural and magnetic properties of magnetite (Fe3O4) nanoparticles is reported. A standard route of co-precipitation was used for the synthesis of undoped and doped magnetite nanoparticles Fe3−xDyxO4 (x=0.0–0.1). Transmission electron microscopy (TEM) shows formation of round shaped particles with diameter in the range of 8–14 nm for undoped sample. On doping beyond x=0.01, the formation of rod like structures is initiated along with the round shaped particles. The number of rods is found to increase with increasing doping concentration. Magnetic characterization using Vibrating Sample Magnetometer (VSM) revealed doping dependent magnetic properties which can be correlated with the crystallite size as determined from X-ray diffraction (XRD). Enhancement in the saturation magnetization in the initial stages of doping can be explained on the basis of incorporation of Dy3+ ions in the inverse spinel structure at the octahedral site in place of Fe3+ ions. Subsequent decrease in saturation magnetization observed beyond x=0.03 could be attributed to precipitation of excess Dy in form of dysprosium ferrite phase.