The ac electrical conductivity for Co-substituted SbNi ferrites

The real ac electrical conductivity sigma(ac)' has been studied for the ferrite system CoxNi5/3-xSb1/3Fe1O4 as a function of frequency, temperature and composition. The experimental results indicate that sigma(ac)' increases with increasing frequency, temperature and Co ion content. sigma(ac)' becomes frequency independent at higher temperatures. The activation energies for electrical conduction and the Curie temperatures decrease with increasing Co ion content. The activation energy for electrical conduction in the ferrimagnetic region decreases as frequency increases. In the power law for ac electrical conductivity (sigma(2)(omega)=B omega(n)), the constant B increases, while the power n of the frequency decreases with increasing Co ion substitution and temperature. An empirical formula for the temperature dependence of n is suggested.