Phase structure refinement, electric modulus spectroscopy, Urbach energy analysis, and magnetic properties of Ce³⁺–Ni²⁺-substituted Y-type barium hexaferrites

In this work, the influence of Ce³⁺–Ni²⁺ substitution on the properties of sol-gel–synthesized Y-type hexaferrites with the following chemical composition is investigated: Ba_2-xCe_xZn_0.7Co_0.7Cu_0.6Fe_12-yNi_yO₂₂ (x = 0.0, 0.4, and 0.6; y = 0.0, 0.5, and 0.7). X-ray diffraction analysis reveals the presence of a few NiFe₂O₄ and Fe₃O₄ secondary phases in the substituted samples (M2 and M3). The Fourier-transform infrared bands at 430, 543, and 582 cm⁻¹ are characteristic bands of iron-oxides, which indicate the vibrations of the octahedral and tetrahedral sites in the S-block of the Y-type hexaferrite. The morphology analysis reveals agglomerated grains, which were generated by weak Van der Waals force and magnetic interaction. The optical analysis reveals the presence of an Urbach energy tail. The electrical properties were investigated based on the Maxwell–Wagner two-layer model and Koop's phenomenological theory. Increase in the magnetization is observed by substituting Fe³⁺ with Ni²⁺ and was studied according to the ligand-field theory.