Impact of rare-earth ions on the physical properties of hexaferrites Ba0.5Sr0.5RE0.6Fe11.4O19, (RE = La, Yb, Sm, Gd, Er, Eu, and Dy)

Abstract

Rare-earth ions RE3+ doped Sr/Ba-hexaferrite nanoparticles were prepared via the sol-gel auto-combustion method. The effect of replacing Fe3+ by RE3+ ions on the structural and morphological properties have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The functional groups were detected by Fourier Transform infrared spectroscopy (FTIR). Hysteresis loops were formed by applying a magnetic field of ± 20 kOe, using vibrating sample magnetometer (VSM). The electric and dielectric parameters; conductivity (σ), dielectric constant (ε′), dielectric loss (ε"), tangent loss (tan δ) were obtained using LCR Meter at frequencies up to 5 MHz and temperature up to 620 K. The XRD analysis showed a pure M-type hexagonal phase with a space group P63/mmc. The Bragg's angle 2θ has been shifted toward lower values by RE3+ addition. Sedimentation of RE3+ ions on the grain boundaries makes barriers for the grain growth, where the size of nanoparticles varies in the range (35.22−51.9 nm). The characteristic FTIR peaks of hexaferrites are obtained between 430 and 595 cm−1. The hexagonal shape shown in the (SEM) images reflects the quality of preparation and uniform distribution of RE3+ ions. (EDX) results showed that there is no significant difference between the theoretical and experimental data for the weight percent of each element. The hysteresis loops give rise to the ferromagnetic nature of the materials at 300 K. Substitution of RE3+ ions with different properties changes the hopping rate of electrons between cations of the same element, which affect the dielectric parameters.