Boost the Crystal Installation and Magnetic Features of Cobalt Ferrite/M-Type Strontium Ferrite Nanocomposites Double Substituted by La(3+) and Sm(3+) Ions (2CoFe(2)O(4)/SrFe(12−2x)Sm(x)La(x)O(19))

Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe(2)O(4)/SrFe(12−2x)Sm(x)La(x)O(19); x = 0.2, 0.5, 1.0, 1.5) nanocomposites were fabricated using the tartaric acid precursor pathway, and the effects of La(3+)–Sm(3+) double substitution on the formation, structure, and magnetic properties of CoFe(2)O(4)/SrFe(12−2x)Sm(x)La(x)O(19) nanocomposite at different annealing temperatures were assayed through X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. A pure 2CoFe(2)O(4)/SrFe(12)O(19) nanocomposite was obtained from the tartrate precursor complex annealed at 1100 °C for 2 h. The substitution of Fe(3+) ion by Sm(3)–(+)La(3+)ions promoted the formation of pure 2CoFe(2)O(4)/SrFe(12)O(19) nanocomposite at 1100 °C. The positions and intensities of the strongest peaks of hexagonal ferrite changed after Sm(3+)–La(3+) substitution at ≤1100 °C. In addition, samples with an Sm(3+)–La(3+) ratio of ≥1.0 annealed at 1200 °C for 2 h showed diffraction peaks for lanthanum cobalt oxide (La(3)Co(3)O(8); dominant phase) and samarium ferrite (SmFeO(3)). The crystallite size range at all constituent phases was in the nanocrystalline range, from 39.4 nm to 122.4 nm. The average crystallite size of SrFe(12)O(19) phase increased with the number of Sm(3+)–La(3+) substitutions, whereas that of CoFe(2)O(4) phase decreased with an x of up to 0.5. La–Sm co-doped ion substitution increased the saturation magnetization (Ms) value and the subrogated ratio to 0.2, and the Ms value decreased with the increasing number of double substitutions. A high saturation magnetization value (Ms = 69.6 emu/g) was obtained using a La(3+)–Sm(3+) co-doped ratio of 0.2 at 1200 for 2 h, and a high coercive force value (Hc = 1192.0 Oe) was acquired using the same ratio at 1000 °C.