Influence of cerium ions on structure-dependent magnetic properties of Ba–Sr M-type hexaferrite nanocrystals

The present study is a systematic effort to investigate the structure-sensitive magnetic parameters of Ce3+ substituted Ba–Sr hexaferrite nanocrystals chemically formulated as Bao .5Sr0.5CexFe12−xO19 where x = 0.0–0.2 with Δx = 0.05. The hexaferrite powders were prepared using the sol–gel self-ignition route and structurally characterized by means of powder X-ray diffraction and Fourier transform infrared spectroscopy. The creation of the M-type hexaferrite phase within the synthesized samples was revealed from the Rietveld refinement of the X-ray diffractograms. The occurrence of a secondary phase of CeO2 was revealed within the hexaferrites for the substitution, x > 0. The refined X-ray diffraction data were utilized to compute the lattice parameters, X-ray density, and lattice parameter ratio. The crystal structure plotted from the refined XRD data reveals the occupancy of the ions at different lattice sites. The XPS data of the hexaferrite were analyzed to confirm the oxidation states of the constituent elements. The nanocrystalline nature of the hexaferrites was revealed from the crystallite sizes calculated using Scherer's formula. The analysis of FTIR spectra confirms that only a fraction of Ce3+ accommodated in the lattice and the remaining Ce content reside in the form of the CeO2 phase. The morphology of the hexaferrites was analyzed from the FESEM profiles of the ferrite samples. The magnetic behavior study was performed by analyzing the Curie temperature, hysteresis loops, and hyperfine interactions by means of susceptibility, V.S.M, and Mössbauer spectroscopy, respectively. The hexaferrites with increasing coercivity, decreasing saturation magnetization, and decreasing Curie temperature are reported in the study. The substituted Ce3+ ions inhibit the grain growth and create lattice imperfections giving rise to hexaferrites with tuned magnetic parameters suitable for different applications.