Structural, magnetic, and magnetocaloric performance of BaFe$_{11.6}$Mg$_{0.05}$Mn$_{0.05}$Ti$_{0.2}$Ni$_{0.1}$O$_{19}$ M type hexaferrite
Résumé
A novel multi-cation substituted M-type hexaferrite, BaFe11.6Mg0.05Mn0.05Ti0.2Ni0.1O19 (BFMMTNO), was synthesized via the conventional solid-state route and sintered at high temperature to explore its structural, morphological, magnetic, and magnetocaloric properties. The partial replacement of Fe³⁺ ions with Mg²⁺, Mn²⁺, Ni²⁺, and Ti⁴⁺ was designed to tailor magnetic anisotropy and enhance magnetic performance. X-ray diffraction confirmed the formation of a single-phase hexagonal magnetoplumbite structure with high crystallinity and an average crystallite size of 87 nm. SEM, TEM, and HR-TEM analyses revealed well-defined grains and excellent lattice ordering. Raman spectroscopy detected subtle lattice distortions arising from multi-site cation substitution, reflecting its influence on the magnetic framework. Mössbauer spectroscopy further confirmed the redistribution of Fe³⁺ ions among the crystallographic sites and revealed a significant reduction in hyperfine magnetic fields induced by multi-cation substitution. Magnetic characterization demonstrated a coercivity of 2.26 kOe, a strong magnetocrystalline anisotropy constant of 7.81 × 10⁵ erg/cm³, and a saturation magnetization of 69.36 emu/g. The compound also exhibited promising magnetocaloric behavior, with a maximum magnetic entropy change (ΔSₘ) of 2.43 J/kg•K and a relative cooling power (RCP) of ~187 J/kg. These findings highlight the effectiveness of multi-cation substitution in tuning the structural and magnetic properties of M-type hexaferrites, underscoring their potential for advanced solidstate magnetic refrigeration applications.
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