Study of structural phase transformation and hysteresis behavior of inverse-spinel α-ferrite nanoparticles synthesized by co-precipitation method

Substitution of cobalt (Co²⁺) ions in cobalt ferrite (CoFe₂O₄) with copper (Cu²⁺) and aluminum (Al³⁺) ions allows variations in their electric and magnetic properties which can be optimized for specific applications. In this article, synthesis of inverse-spinel Co_1−xCu_xFe_2−xAl_xO₄ (0.0 ≤ x ≤ 0.8) nanoparticles by substituting Cu²⁺ and Al³⁺ ions in CoFe₂O₄ via co-precipitation method is reported. By controlling copper and aluminum (Cu-Al) substituent ratio, the magnetic moment and coercivity of synthesized cobalt ferrite nanoparticles is optimized. The role of substituents on the structure, particle size, morphology, and magnetic properties of nano-crystalline ferrite is investigated. The Co_1−xCu_xFe_2−xAl_xO₄ (0.0 ≤ x≤ 0.8) nanoparticles with crystallite size in the range of 23.1–26.5 nm are observed, 26.5 nm for x = 0.0–23.1 nm for x = 0.8. The inverse-spinel structure of synthesized Co_1−xCu_xFe_2−xAl_xO₄ (0.0 ≤ x ≤ 0.8) nano-particles is confirmed by characteristic vibrational bands at tetrahedral and octahedral sites using Fourier transform infrared spectroscopy. A decreases in coercive field and magnetic moment is observed as Cu-Al contents are increased (x = 0.0–0.8). The positive anisotropy of synthesized particles Co_1−xCu_xFe_2−xAl_xO₄ (0.0 ≤ x ≤ 0.8) is obtained in the range 1.96 × 10⁵ J/m³ for x = 0.0 to 0.29 × 10⁵ J/m³ for x = 0.8.