الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
Spinel ferrites have been a subject of great interest both due to the special combination of their physical properties and characteristics determined in numerous studies and their important technological applications . The electric and magnetic properties of these · ferrites arise largely from their structural features and the nature of distribution of the ions in the sublattices .
In this thesis one of these materials is used, trivalent chromium have been substituted for trivalent iron in the stoichiometric nickel ferrite. Six samples of the composition NiCrxFe2_x 04 (0.0 < x :”:: 1.0) are synthesized using the ceramic
sintering technique. X-ray powder diffraction pattern carried
out at room temperature shows a single-phase spinel structure with no evidence of impurities. The lattice parameter a obtained from these patterns was found to be decreased linearly with chromium content in accord to Vegard’s rule.
Electrical properties (electrical conductivity, dielectric constant and dielectric loss tangent)are studied at the temperature range (290-850k) and frequency rang(l02 -l05 Hz). The experimental results indicate that for all prepared samples, ac conductivity is increased as the frequency and temperature
are increased. At high temperature the conductivity becomes
frequency independent. temperatures decrease conductivity behaviour interpreted due to the
The obtained magnetic transition as the Cr ion substitution. The of these compounds could be presence of d.c conductivity which