Structure and magnetic properties of coprecipitated nickel-zinc ferrite doped rare earth elements of Sc, Dy, and Gd

This research is the basic study of temperature-sensitive ferrite characteristics prepared by coprecipitation with doping different sizes of rare earth elements. Ni0.5Zn0.5RExFe2-xO4 (NZRF) (x = 0.02, 0.05, 0.07, and 0.09) nanoparticles (NPs) doped by Sc, Dy, and Gd prepared by chemical coprecipitation method. XRD results show that the grain size of Ni0.5Zn0.5RExFe2-xO4 is from 10.6 to 12.4 nm, which is close to the average grain size of 13.9 nm observed on TEM images. It is also found that the ferrite particles are spherical and slightly agglomerated in TEM images. FTIR results show that the NZRF has the characteristic stretching of tetrahedral and octahedral sites in spinel ferrite near 580 cm−1 and 418 cm−1. The concentrations of nickel, zinc, iron, and rare earth elements have been determined by ICP-AES, and all ions have participated in the reaction. The magnetic properties of Sc3+, Dy3+, and Gd3+-doped NZRF NPs at room temperature are recorded by a physical property measurement system (PPMS-9). It is found that the magnetization can be changed by adding rare-earth ions. All the samples exhibit very small coercivity and almost zero remanences, which indicates the superparamagnetism of the synthesized nanoparticles at room temperature (RT). When x = 0.07, Gd3+-doped Ni0.5Zn0.5Fe2O4 (NZF) exhibits the highest saturation magnetization. Magnetic properties of NZGd0.07 vary the most with temperature. The thermomagnetic coefficient of NZGd0.07 nanoparticles stabilized to 0.18 emu/gK at 0–100 °C. Hence, NZGd0.07 with low Curie temperature and the high thermomagnetic coefficient can be used to prepare temperature-sensitive ferrofluid for hyperthermia.