Comprehensive analysis of the synthesis and characterizations of Cr-substituted Cd-Cu ferrite: Insights from Mössbauer and impedance spectroscopy

Abstract

This work explores the influence of chromium ion substitution on the dielectric characteristics of Cd_0.5Cu_0.5Cr_xFe_2-xO₄ magnetic ferrite prepared by the coprecipitation method and sintered at 1000 °C. X-ray diffraction (XRD) and Rietveld refinement analysis ensured the purity and crystallinity of the formed spinel structure. The ionic radius of cations affects the cation distribution, particularly the occupation of large cadmium ions at the tetrahedral sites. The lattice parameter, oxygen position parameter, and bond length decrease by adding Cr³⁺ ions, while the vibrational frequency and force constant increase. This leads to the reinforcement of interatomic bonds and increases the elastic moduli and Debye temperature. Therefore, chromium-doped ferrites are relatively rigid compared to the others. Mössbauer spectroscopy detected the hyperfine magnetic parameters, including isomer shift (I_S), quadrupole splitting (Qs), magnetic field strength, and the relative area between tetrahedral and octahedral sites. The two well-defined sextets represent the ferromagnetic behavior of the samples x = 0.1, 0.2, and 0.4, while the sample Cr 0.8 exhibits a doublet type, demonstrating superparamagnetic behavior. All the dielectric parameters decrease by adding Cr ions. Impedance spectroscopy provides valuable information about the resistances and capacitances of the grain and grain boundaries. The equivalent circuit of the samples consists of two series RC parallel circuits according to the semicircles obtained from the Nyquist plot. The calculated activation energy and relaxation time further explain the nature of charge carriers' movement within the material. These findings indicate that these samples are good candidates in advanced electronic and magnetic devices and high-frequency applications.