Magnetic Attributes of NiFe(2)O(4) Nanoparticles: Influence of Dysprosium Ions (Dy(3+)) Substitution

This paper reports the influence of dysprosium ion (Dy(3+)) substitution on the structural and magnetic properties of NiDy(x)Fe(2−x)O(4) (0.0 ≤ x ≤ 0.1) nanoparticles (NPs) prepared using a hydrothermal method. The structure and morphology of the as-synthesized NPs were characterized via X-ray diffraction (XRD), scanning and transmission electron microscope (SEM, and TEM) analyses. (57)Fe Mössbauer spectra were recorded to determine the Dy(3+) content dependent variation in the line width, isomer shift, quadrupole splitting, and hyperfine magnetic fields. Furthermore, the magnetic properties of the prepared NPs were also investigated by zero-field cooled (ZFC) and field cooled (FC) magnetizations and AC susceptibility measurements. The M(ZFC) (T) results showed a blocking temperature (T(B)). Below T(B), the products behave as ferromagnetic (FM) and act superparamagnetic (SPM) above T(B). The M(FC) (T) curves indicated the existence of super-spin glass (SSG) behavior below T(s) (spin-glass freezing temperature). The AC susceptibility measurements confirmed the existence of the two transition temperatures (i.e., T(B) and T(s)). Numerous models, e.g., Neel–Arrhenius (N–A), Vogel–Fulcher (V–F), and critical slowing down (CSD), were used to investigate the dynamics of the systems. It was found that the Dy substitution enhanced the magnetic interactions.