Efeito da dopagem do íon Ti⁴⁺ sobre as propriedades estruturais, magnéticas e elétricas na hexaferrita de bário sintetizada por coprecipitação

Abstract

This study investigates the influence of Ti⁴⁺ ion doping on the structural, elastic, magnetic, and electrical properties of M-type barium hexaferrite, BaFe₁₂₋ₓTiₓO₁₉ (0.0 ≤ x ≤ 0.9), synthesized via the coprecipitation method. X-ray diffraction combined with Rietveld refinement confirmed a single-phase magnetoplumbite structure, with systematic changes in lattice parameters and unit cell volume—lattice expansion for 0.0 ≤ x ≤ 0.3 and contraction for higher Ti⁴⁺ content—attributed to the selective Fe³⁺ → Ti⁴⁺ substitution at specific sites of the crystal structure. FTIR spectroscopy revealed shifts in vibrational bands, variations in the force constants for octahedral and tetrahedral sites, and an increase in the Debye temperature with increasing Ti⁴⁺ concentration. The elastic moduli were estimated using the Debye theory for a hexagonal crystal structure. The magnetic properties, determined by the law of approach to saturation and the Stoner–Wohlfarth model, showed a reduction in saturation magnetization, remanence, coercivity, as well as in the anisotropy constant and field with increasing Ti⁴⁺ concentration, due to the weakening of superexchange interactions, cationic disorder, and the reduction in particle size. The dielectric and electrical transport properties, assessed by complex impedance spectroscopy, were interpreted using the modified Debye, Kohlrausch–Williams–Watts (KWW), and Jonscher models, indicating non-Debye relaxations driven by interfacial polarization and small polaron hopping conduction. Variations in cation distribution among the different crystallographic sites significantly affected all the analyzed physical properties. The results demonstrate that Ti⁴⁺ doping enables fine-tuning of the electromagnetic behavior, highlighting barium hexaferrite as a promising material for multifunctional device applications.