Influence of Gd and Ni doping on the structural, morphological, and magnetic properties of M-type calcium hexaferrite

Abstract

In this study, our aim was to synthesize Gd–Ni doped M-type calcium hexaferrites using a solid-state reaction method. The chemical composition of the synthesized material was Ca_1−xGd_xFe_12−yNi_yO₁₉, (0.00 ≤ x, y ≤ 0.07). This study focused on examining the impact of low concentrations of Gd³⁺ and Ni²⁺ ions in the formula. The M-type hexagonal structure was confirmed with high certainty using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. In addition, a minor impurity phase, α-Fe₂O₃, was detected. Field-emission scanning electron microscopy (FESEM) analysis focused on examining the surface morphology of the sample, and the obtained images revealed the presence of anticipated grain sizes ranging from 0.80 to 1.06 μm. This study employed energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) to validate the elemental composition and oxidation states of the constituent elements. A vibrating sample magnetometer (VSM) and theoretical calculations are used to determine crucial parameters, including remanent magnetization (M_r), coercivity (H_c), saturation magnetization (M_s), squareness ratio (M_r/M_s ≤ 0.5), magneton number (μ_B), and magneto-crystalline anisotropy constant (K_a). Examination of these parameters contributes to a deeper understanding of the magnetic properties under investigation. This paper presents an analysis of the obtained samples, highlighting their remarkable suitability for applications in high-frequency devices and high-density recording media.