Abstract
This paper reports the influence of dysprosium ion (Dy3+) substitution on the structural and magnetic properties of NiDyxFe2−xO4 (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. 57Fe Mössbauer spectra were recorded to determine the Dy3+ 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 MZFC (T) results showed a blocking temperature (TB). Below TB, the products behave as ferromagnetic (FM) and act superparamagnetic (SPM) above TB. The MFC (T) curves indicated the existence of super-spin glass (SSG) behavior below Ts (spin-glass freezing temperature). The AC susceptibility measurements confirmed the existence of the two transition temperatures (i.e., TB and Ts). 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.
Highlights
Nanosized Ni-spinel ferrites have widely been used in magnetic storage media, magnetic adsorbents, telecommunication, catalysts, microwave absorbers, and computer memories [1,2,3,4,5]
Irrespective of Dy3+ contents, all the X-ray diffraction (XRD) peaks have been verified to the cubic nanosized Ni-spinel ferrites (JCPDS Card Number 54-0964), indicating the lattice site compatibility of the Dy3+ ions in the Ni spinel ferrite structure in the absence of any impurity
The inset (Figure 3) displays the selected angle electron diffraction (SAED) patterns of the corresponding sample that confirmed the agglomeration of single crystalline Ni spinel ferrite nanoparticles
Summary
Nanosized Ni-spinel ferrites have widely been used in magnetic storage media, magnetic adsorbents, telecommunication, catalysts, microwave absorbers, and computer memories [1,2,3,4,5]. The structural and magnetic characteristics of nanosized Ni-spinel ferrites have been enhanced by substituting varieties of magnetic, nonmagnetic, and rare earths ions [6,7,8]. Modified magnetic properties of Erbium (Er3+) and Samarium (Sm3+) substituted nickel ferrites were analyzed by low temperature magnetization, and zero-field cooled and field cooled (ZFC-FC) measurements. Such samples revealed a superparamagnetic (SPM) behavior with very low coercivity (Hc) and remanence magnetization (Mr), making them suitable for developing soft magnets [10]. To the best of our knowledge, there is no study reporting the Mossbauer, zero-field cooled (ZFC), and field cooled (FC) magnetizations and AC susceptibility measurements for Dy substituted nanoparticles of Ni spinel ferrites.
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