High Magneto-Crystalline Anisotropic Core–Shell Structured Mn0.5Zn0.5Fe2O4/Polyaniline Nanocomposites Prepared by in Situ Emulsion Polymerization

Nanosized Mn0.5Zn0.5Fe2O4 ferrite particles were synthesized by a reverse microemulsion reaction process. Core–shell nanocomposites composed of Mn0.5Zn0.5Fe2O4 nanocrystals and conjugated polymer polyaniline were successfully synthesized from a simple and inexpensive process, and in situ chemical oxidative polymerization of aniline occurs. Mn0.5Zn0.5Fe2O4 nanocrystals are in the micellar solution of dodecyl benzene sulfonic acid (DBSA). It acts as both a surfactant and a dopant. These nanocomposites were subsequently investigated for structural, morphological magnetic, and electromagnetic properties. Transmission electron microscopy (TEM) studies reveal the formation of core–shell type morphology with ferrite nanocrystals (∼9–11 nm) as the center, while the polymer (PANI) formulates the outer shell of the composite. A decrease in the blocking temperature of Mn0.5Zn0.5Fe2O4 nanocrystals after coating with PANI has been recorded, attributing that the polymer matrix allows each ferrite nanoparticle to behave independently, indicating a decrease in the dipole–dipole interactions that will decrease the anisotropy energy barrier. Magnetic properties of the synthesized nanoferrite exhibit a very high magneto-crystalline anisotropy energy value of 31.3 × 105 erg/cm3 at a blocking temperature of 90 K. The complex permittivity, permeability, and microwave absorption properties of the composites were explored in the 8.2–12.2 GHz (X-band) frequency range. The nanocomposites are observed to show high shielding effectiveness (SEA = 31.2 dB) as compared to pure PANI, which strongly depends on dielectric loss, magnetic permeability, and volume fraction of Mn0.5Zn0.5Fe2O4 nanocrystals. The high value of SEA suggests that these composites can be used as a promising electromagnetic absorbing material.