الفهرس 
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Abstract
In this work, a series of (x) BaTiO3 / (1-x) Ni0.5Zn0.5Fe2O4 nanocomposite samples were prepared using citrate autocombustion and the samples were classified into three groups.
In first group: A series of (x) BaTiO3 / (1-x) Ni0.5Zn0.5Fe2O4 ; 0.0 x 1.0 were prepared by double sintering technique and citrate autocombustion method in comparison study due to different characterization analysis. The comparison reveals that from X-ray diffraction; all the samples from the two methods formed in single phase in both; cubic spinel structure NiZnFe2O4 (NZF) ferrite and perovskite tetragonal structure BaTiO3 (BTO). The crystallite size (L) of the two phases was obtained from ceramic method of NZF and BTO is 68nm and119nm respectively. While from citrate autocombustion method, the crystallite size (L) is around 30 nm and 47nm. The values of lattice constant and d- spacing, and Miller indices were calculated and reported. It was found that the ratio of BTO (x=0.5) is a critical concentration. from FT- IR spectra of the samples, the spectral frequencies of the vibrational bands of different methods are reported. The IR spectral analysis of the two group’s samples reveals the formation of spinel and perovskite structure. The scanning electron microscopy (SEM) and the hysteresis measurements were carried out to determine saturation magnetization (Ms), remnant magnetization (Mr) and coercivity (Hc) of the samples. The variation of the magnetic susceptibility (χM) behavior with temperature as a function of field intensity was also studied, where the magnetic constants were calculated and reported. The variation of dielectric constant (’), dielectric loss factor (”) and the ac electrical conductivity (σac) of 0.5BaTiO3 / 0.5Ni0.5Zn0.5Fe2O4 magnetoelectric nanocomposite has been investigated as a function of both frequency and temperature. Thermal hysteresis (first-order transition) was occurred when the experimental data were collected during heating (300-830 K) and cooling (830-300 K) processes. The exact transition temperature and the amount of thermal hysteresis are dependent on the applied ac electric field. Therefore the area of the thermal hysteresis loop in between the two branches for the nanocomposite is a frequency dependent; it decreases as the frequency increases. The delay (lagging) time between heating and
cooling processes was estimated from the hysteresis loop area versus frequency.
The dielectric conduction mechanisms in the investigated nanocomposite were
explained according to different models. The observed values of Seebeck
coefficient indicate that the conduction is due to electron hopping mechanism which
is agreement with that obtained from dielectric measurements. This study enhances
the use of multiferroic system in the memory applications. ), this is a clear
application on the so called dynamic random access memories (DRAM) which are
being used in today‘s computers. This result gives information about how our work
is applicable in high technology.