Correlation between structure and physical properties in Cu/Al-substituted barium hexaferrites ((Ba1–xCux)(AlxFe12–x)O19; x = 0.0 to 1.0)

This study investigated the structural, magnetic, optical and vibrational properties of (Ba_1–xCu_x)(Al_xFe_12–x)O₁₉ hexaferrite nanoparticles synthesized by a simple wet-chemical c-precipitation method at the substitution level of x = 0.0–1.0. X-ray diffraction confirmed a single-phase hexagonal structure with lattice compression attributed to the smaller ionic radii of Cu²⁺ and Al³⁺. The crystallite size remained consistent at approximately 120 nm across the samples. Magnetic analysis revealed superparamagnetic behaviour at higher substitution levels, with decreased magnetization and coercivity resulting from site-specific occupation by Al³⁺ and Cu²⁺ ions. Nonlinear optical measurements using the Z-scan technique at 532 nm have shown a strong optical limiting behavior with two-photon absorption coefficients ranging from 6.3 × 10⁻¹¹ to 9 × 10⁻¹¹ m/W, underscoring their potential for photonic applications. FTIR spectroscopy confirmed metal–oxygen bond vibrations and the band shifts consistent with cationic substitution. These results highlight the tunable multifunctionality of Cu/Al-substituted Ba-hexaferrites, making them promising candidates for magnetic and optoelectronic devices.