Microstructural and Magnetic Properties of La-Ce co-Doped Soft-Hard Ferrites Synthesized by the Co-precipitation Method

Abstract

Hexaferrites’ magnetic and structural properties are highly sensitive to changes in sintering temperature and cationic replacements. We report the phase, microstructural analysis, and magnetic behavior of La-Ce co-doped ferrites with a wide range of compositions, including strontium ferrite [SrFe_12-x(La_0.5Ce_0.5)_xO₁₉] and cobalt ferrite [CoFe_2-x(La_0.5Ce_0.5)_xO₄] with varying La-Ce contents (x = 0.0–0.4) using a modified co-precipitation method at room temperature. The results confirmed the hexagonal and cubic structure for La-Ce co-doped strontium and cobalt ferrite compounds, respectively. Morphological studies show particles with a rod-like to plate-like morphology, featuring irregular edges and a moderate degree of agglomeration, suggesting anisotropic grain growth. The lattice parameters a (lattice constant in the basal plane) and c (lattice constant along the vertical direction) for strontium ferrite decrease from 5.84 to 5.20 Å and 23.01 to 21.92 Å, respectively, while for cobalt ferrite they increase from 8.29 to 8.38 Å. The optimum magnetic investigations include saturation magnetization (M_s), remanent magnetization (M_r), and coercivity (H_c) up to 71.6 emu/g, 30 emu/g, 1284 Oe, and 39 emu/g, 16 emu/g, and 349 Oe with 10% La-Ce substitution for Fe in strontium and cobalt ferrite, respectively. Thirty percent La-Ce substitution for Fe in cobalt ferrite results in an unexpected increase in M_s (50.92 emu/g) and M_r (20.86 emu/g) that could be attributed to the cation redistribution. The M_r/M_s ratio decreases with the increase of La-Ce contents in both compounds, which is attributed to the reduced exchange interaction between magnetic particles. The moderate values of magnetic parameters make them suitable for permanent magnets in motors and generators, loudspeakers, and audio equipment.