الفهرس 
Theoretical backgroundOnly 14 pages are availabe for public view
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Abstract
Multiferroic nano-composites with chemical formula (x) Ni0.5Mg0.5Fe2O4 (NMFO) + (1-x) BaTiO3 (BTO); (x=10, 20, 30 and 40%) were prepared via sol–gel method.
X-ray diffraction (XRD) analysis of (NMFO) phase exhibits a single cubic phase of spinel while (BTO) exhibits a single tetragonal phase of perovskite. XRD of all composite samples showed the coexistence of both phases (cubic and tetragonal). Furthermore, the lattice parameters and crystallite size were calculated. The lattice parameters for (NMFO), (BTO) and their composites are nearly constant which indicates that there is no chemical reaction between constituents. In composite samples, the crystallite size of (NMFO) phase increases while that of (BTO) phase decreases with increasing x-content. High resolution transmission electron microscope (HRTEM) revealed the formation of nano-particles for both (NMFO) and (BTO) phases with average particle size 9 nm and 67 nm, respectively. Moreover, there is a single particle domain for (NMFO) phase where the crystallite size and the average particle size are nearly equal. Field emission scanning electron microscope (FESEM) confirmed that the average grain size increases with increasing x-content. D.C resistivity confirmed the semiconductor behavior of all samples where the resistivity decreases with increasing temperature. Furthermore, Curie temperature (Tc) of all samples were determined from resistivity curves. On the other hand, D.C resistivity decreases by increasing x-content. Electrical permittivity of all samples were examined as a function of frequency in both low and high frequency ranges.
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Low frequency permittivity exhibits the normal dispersion behavior of Koop’s model while
high frequency permittivity exhibits the resonance phenomenon where the resonant frequency increases with increasing x-content. Pure (BTO) sample and its composites exhibit ferroelectric hysteresis loops. Maximum polarization (Pmax) and maximum electric field applied (Emax) were calculated from the hysteresis loops where (Pmax) and (Emax) decreases with increasing x-content. Pure (NMFO) sample and its composite exhibit well saturated ferromagnetic hysteresis loops. Saturation magnetization (Ms) and coercive magnetic field (Hc) were calculated from the hysteresis loops where (Ms) increases with increasing x-content. On the other hand, relative magnetic permeability (μr) was studied. It was concluded that (μr) increases with increasing x-content. Moreover, there is a magnetic cooperative phenomenon between (NMFO) phase and (BTO) phase in temperature range (380oC – 480oC).