Magnetic, Dielectric and Ethanol Gas Sensing Properties of Poly(o-phenylenediamine)/(MnNi)Fe<inf>2</inf>O<inf>4</inf> Nanocomposites and Quantum Chemical Calculations of (MnNi)Fe<inf>2</inf>O<inf>4</inf>

(MnNi)Fe2O4 nanoparticle was prepared by auto-combustion method and its composites with poly(o-phenylenediamine) (PoPD) were synthesized through in-situ oxidative polymerization method. FTIR and XRD studies confirmed the formation of PoPD/(MnNi)Fe2O4 nanocomposites. The crystalline size of PM1, PM2 and PM3 are 44 nm, 45 nm and 16 nm respectively. The dispersion of (MnNi)Fe2O4 nanoparticles in PoPD reduces their crystalline size. In PoPD/(MnNi)Fe2O4 nanocomposites, spherical morphology of PoPD is modified by (MnNi)Fe2O4 nanoparticles. TEM images showed that (MnNi)Fe2O4 nanoparticles are dispersed in PoPD matrix. The hysteresis loops of (MnNi)Fe2O4 nanoparticles and PoPD/(MnNi)Fe2O4 nanocomposites indicated that they are ferrimagnetic in nature. The saturation magnetization value of (MnNi)Fe2O4, PM1, PM2 and PM3 are 29.871 emu/g, 3.342 emu/g, 4.298 emu/g and 7.877 emu/g respectively. The thermal stability and saturation magnetization value of PoPD/(MnNi)Fe2O4 nanocomposites increases with increase in concentration of (MnNi)Fe2O4 nanoparticles. Dielectric properties of PoPD/(MnNi)Fe2O4 nanocomposites were studied at different frequencies and temperature. The Mn2+ substitution in NiFe2O4 has improved the ethanol sensitivity of PoPD/(MnNi)Fe2O4 nanocomposites. The dielectric constant of PoPD/(MnNi)Fe2O4 nanocomposites increases with increase in frequency, temperature and concentration of nanoparticles. Theoretical investigations of the metal oxide complex were done by utilizing a DFT/ B3LYP/LANL2DZ basis set. The optimized bond parameters (bond lengths, bond angles and dihedral angles) were determined using identical level of basis set. The NLO properties of the title compound was calculated using first-order hyperpolarizability calculation. The HOMO-LUMO, which clarifies the possible charge transfer, happens inside the molecule.