Abstract. The real AC electrical conductivity was studied as a function of frequency f, temperature T and composition x for a series of samples prepared using the double-sintering ceramic technique. The experimental results indicated that increases as the temperature and frequency increase and as the Ni ion substitution decreases. The Curie temperature and the activation energy for electrical conduction ( in the paramagnetic and in the ferrimagnetic region) increase as the Ni ion substitution increases. decreases while increases as the frequency increases and they become frequency-independent above the Curie temperature. The parameters n and B in the power law for were found to be composition- and temperature-dependent. n decreases while B increases as temperature increases. Both n and B decrease as the Ni ion substitution increases. Empirical formulae were suggested for the temperature-dependences of n and B.

Print publication: Issue 3 (14 March 1996)
Received 19 January 1995, in final form 9 November 1995