Magnetite nanoparticles doped with rare earth ions: synthesis, structural, and magnetic properties

Abstract

Taking into account the practical signiﴐ- cance of magnetite nanoparticles, several nanostruc- tured magnetite samples with doping of 2.5% Sm, Dy, La, and Lu rare earth ions were synthesized using the co-precipitation method. The structural and magnetic properties of the obtained doped nanoparticles were investigated in detail using transmission electron microscopy, X-ray di럿raction, small-angle X-ray scat- tering, and magnetic measurements. All the doped nanostructured magnetite samples have a cubic phase with spinel crystal structure Fd 3 m; a nanoparticle size is ranging from 20 to 32 nm. Changes in the char- acteristic Fe–O bond lengths indicated that the doping rare earth ions mainly occupy octahedral sites in the oxygen unit. The size of the nanoparticles depends on the type of doped rare earth due to di럿erence in ionic radius. Neutron di럿raction data indicated that the magnetic structure of doped magnetite nanoparticles is ferrimagnetic. The magnetic measurements showed a superparamagnetic state in all the doped magnetite nanoparticles. It is assumed that noticeable changes in the structural and magnetic properties of magnetite nanoparticles compared to bulk matter are primarily associated with a defect-rich structure on the surface of those nanoparticles and the e럿ect of rare earth ions doping on it.