Tailoring magnetic and dielectric properties of SrFe12O19/NiFe2O4 ferrite nanocomposites synthesized in presence of Calotropis gigantea (crown) flower extract

SrFe<inf>12</inf>O<inf>19</inf> (M-type hexaferrite) and NiFe<inf>2</inf>O<inf>4</inf> (spinel) nano ferrite powders were synthesized in the presence of Calotropis gigantea (crown) flowers extract separately. SrFe<inf>12</inf>O<inf>19</inf>/NiFe<inf>2</inf>O<inf>4</inf> nanocomposites were prepared in the presence of crown flowers extract and the effect of different weight ratios (M:S – 9:1, 8:2, 7:3, 6:4, 5:5) on structural, microstructural, magnetic, electrical transport, and dielectric properties were studied. The average crystallite size of nanocomposites was found from 25 nm to 44 nm. In addition, it was observed that the crystallite size of the M-phase decreased when the spinel phase increased. XRD analysis depicts the presence of both M and S phases in composites. The M-H loops analysis of SrFe<inf>12</inf>O<inf>19</inf>/NiFe<inf>2</inf>O<inf>4</inf> composites indicates that the coercivity (3181–326 Oe), and saturation magnetization (57.5 Am²/kg. - 40 Am²/kg.) decreased when the spinel phase amount increased. Nanocomposites with weight ratios 9:1, 8:2, 7:3, 6:4 belong to a hard ferrite, while 5:5 shows soft magnetic nature. However, prepared composites possess a multi-domain structure. The weak exchange coupling interactions were found in composites 9:1 and 8:2, whereas the partial exchange coupling interactions were observed in composites 7:3, 6:4, and perfect exchange coupling interaction was noticed in 5:5.