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

Nanosized Mn 0.5 Zn 0.5 Fe 2 O 4 ferrite particles were synthesized by a reverse microemulsion reaction process. Core–shell nanocomposites composed of Mn 0.5 Zn 0.5 Fe 2 O 4 nanocrystals and conjugated polymer polyaniline were successfully synthesized from a simple and inexpensive process, and in situ chemical oxidative polymerization of aniline occurs. Mn 0.5 Zn 0.5 Fe 2 O 4 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 Mn 0.5 Zn 0.5 Fe 2 O 4 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 × 10 5 erg/cm 3 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 (SE A = 31.2 dB) as compared to pure PANI, which strongly depends on dielectric loss, magnetic permeability, and volume fraction of Mn 0.5 Zn 0.5 Fe 2 O 4 nanocrystals. The high value of SE A suggests that these composites can be used as a promising electromagnetic absorbing material.