Synthesis and Characterization of CaFe1.925Gd0.025Sm0.05O4/PEG Core–Shell Nanoparticles for Diverse Applications

Abstract

The core–shell structure has been studied by coating polyethylene glycol (PEG) on rare-earth-doped calcium ferrite nanoparticles (RCFNPs). RCFNPs are successfully synthesized in the formula CaFe_1.925Gd_0.025Sm_0.05O₄ by the citrate nitrate auto-combustion method. The XRD pattern of PEG-coated RCFNPs observed two peaks at 19.3° and 23.6° confirming the existence of PEG, while the other peaks are attributed to the orthorhombic structure formation. The obtained samples exhibit an orthorhombic single-phase structure with an average crystallite size in the range of 18–20 nm. The elemental analysis is performed using EDAX and XPS. The doublet spectrum of Fe atoms corresponds to the valence states Fe 2P_1/2 and Fe 2P_3/2. High-resolution transmission electron microscopy (HRTEM) revealed a well-designed hexagonal core/shell structure represented as a unique hexagonal PEG shell coating the synthesized RCFNPs. The magnetic hysteresis loops have been recorded using VSM. The coupling between the unpaired electrons of Fe⁺³ and Sm⁺³ ions via the p orbitals of the O⁻² ions leads to the antiferromagnetic alignment. The smaller values of the switching-field distribution (SFD) and higher coercivity of the prepared samples are most appropriate for ultra-high-density recording performance. The behavior of dielectric parameters is explained on the basis of the interfacial polarization and the Maxwell–Wagner polarization models. Diffuse reflectance spectroscopy (DRS) is used to study the performance of electromagnetic reflection and estimate the optical band gaps of the samples. The obtained data shows that the coating has an important role in enhancing the reflection by up to 50%.