Influence of rare earth ion substitutions on the structural,optical, transport, dielectric, and magnetic properties of superparamagnetic iron oxide nanoparticles

摘要

Superparamgnetic Fe304 and RE＇Fe304 （RE = Dy, Nd, La） nanoparticles with an averagecrystallite size in the range of 15-24 nm, were synthesized by co-precipitation method. The sampleswere characterized using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, vibratingsample magnetometer （VSM）, UV-Vis spectroscopy, LCR bridge, and two-probe technique. X-raydiffraction patterns of all the investigated samples reveal the typical phase of magnetite structure, witha small contribution of orthoferrite （NdFeO3） as a secondary phase in Nd：Fe3O4 sample. Thesaturation magnetization （Ms ） of the samples has values in the range from 41.8 to 52.3 emu/g, anddecreases with RE ion doping depending on the ionic radius. Negligible values of the coercivityHe and remanence Mr, indicate the superparamagnetic nature of the investigated samples. Thecalculated values of indirect optical band gap of Fe3O4 and RE：Fe3O4 nanoparticles are in the range of 0.9-1.25 eV. The dielectric constant of the samples decreases, while their activation energy increaseswith the increasing of ionic radii of dopants.