Structural and magnetic properties of CaMg2Fe16O27

A new compound, CaMg2Fe16O27, is synthesized for the first time, in polycrystalline form, using stoichiometric mixture of oxides with standard ceramic technique and characterized by X-ray diffraction, It is found to have a hexagonal W-type structure with lattice parameters alpha = 5.850 Angstrom and c = 33.156 Angstrom, Electrical studies show that the compound is a semiconductor with energy of activation, DeltaE = 0.56 eV. Electrical conductivity results show a transition in the conductivity vs temperature plot near the Curie temperature. The activation energy value obtained for the paramagnetic phase is found to be higher than that of the ferrimagnetic phase. The molar magnetic susceptibility was measured in the temperature range 300-850 K and the results show that the compound is ferrimagnetic at room temperature. The compound also shows hysteresis at 300 K, paramagnetic nature of the sample above Curie temperature is also studied. The Curie molar constant C-M calculated from the plot of 1/chi (M) vs T(K) is found to be nearly in agreement with the expected value.