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A series of Li0.5 Fex Ga2.5 - x O4 systems were prepared for x = 0, 0.25, 0.5, 0.75 and 1 by the general ceramic method. X-ray diffraction showed that all compositions have single phase Spinel cubic structure. The lattice parameter increased with enhancing iron concentration. The thermoelectric coefficient decreased with increasing x, and the majority carriers are holes. The increase of the jump length of hole increased the electrical conductivity. Jump-length increased with iron concentration and the rate of jumping gave rise to the electrical conductivity. The concentration of Fe3 + ions in Lithium gallate is important, for such structures may have application in communication technology.

A series of Co-Zn ferrite samples substituted by Mn were prepared by the usual double sintering ceramic technique. The x-ray diffraction patterns of the samples confirmed the formation of single-phase spinel structure, and x-ray analysis supply data that suggests the cation distribution of the material. The tetrahedral and octahedral radius permits one to calculate the theoretical lattice parameter and the bond lengths Fe-O at A and B sites. The particle size of the given samples was measured from the Scherer equation and a correlation was found between particle size, and structural and magnetic properties. The XRF confirmed the presence of stoichiometric solid-state reaction in the material. The saturation magnetization Ms decreases continuously with increase of Mn content. For Co0.6 Zn0.4 Mnx Fe2 - x O4 , the Neel model for the two sub-lattice can be used up to x = 0.8 to explain the compositional variation of magnetic moment due to the reduction of the A-B interaction. Above x = 0.8, the reduction of the B-B interaction is responsible for an increase in the magnetic moment due to the canting effect.