M.U. Rana

EFFECT OF Mg2+ SUBSTITUTIONS ON THE STRUCTURAL AND MAGNETIC PROPERTIES OF Co–Mg W-TYPE HEXAGONAL FERRITE

W-type hexagonal ferrites having the formula BaCo2-xMgxFe16O27 with x = 0, 0.4, 0.8, 1.2, 1.6, 2.0 were synthesized by the chemical coprecipitation method. XRD analysis shows that the structure of all the compositions is W-type hexagonal ferrite. The c/a ratio varies from 5.48 to 5.52, consistent with the standard values. It was observed that the bulk density and X-ray density decrease whereas porosity increases with increasing concentration of Mg2+. Room temperature resistivity increases, from 103 to 107 (Ω cm) by increasing the concentration of Mg2+, due to an increased number of grain boundaries. The remanence and saturation magnetization decrease with increasing Mg2+ content while coercivity increases as the Mg2+ increases according to the relation Hc ∝ 1/r. The measured coercivity values are suitable for use in high frequency applications such as microwave absorber materials.

EMPIRICAL ESTIMATES OF PHYSICAL PARAMETERS FROM ELECTRICAL RESISTIVITY MEASUREMENTS ON FERRITES

Measurements on the electrical resistivity of Mn1−xZnxFe2O4 ferrites with 0<x< 0.15 in the temperature range 300 K<T<450 K, have been carried out. Analysis of the normalised electrical resistivity of these ferrites shows deviations from linearity both at low and high temperatures. There exists a deviation in the electrical resistivity at 300 K at high zinc concentration which may be due to hopping of electrons between Fe+2 and Fe+3 ions at octahedral sites.