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Samples with the chemical formula Cu0.5Zn0.5Fe2−xRxO4 (R = La, Nd, Sm and Gd; x = 0 and 0.1) were prepared by the standard ceramic method. The real part of the dielectric constant ε′ and the ac electrical conductivity σac are measured and the dielectric loss tangent tan δ is calculated in the frequency range 50–105 Hz and from room temperature up to ≅800 K. ε′ and tan δ are found to decrease with increasing the frequency while σac is generally increased. On the contrary ε′, σac and tan δ are increased with temperature. No relaxation was detected in tan δ(f) in the investigated frequency range while tan δ(T) showed two maxima. The composition dependence of the dielectric parameters is discussed and the results are explained using Koops's model. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The effect of Zr-substitution on the physical and magnetic properties of Li 0.3+0.5x Zn 0.4 Zr x Fe 2.3-1.5x O 4 ferrites (x=0.0, 0.01, 0.02, 0.03 and 0.05), prepared by the standard ceramic method, has been studied. It is found that the saturation magnetization increases up to x=0.02 and then it decreases. On the other hand, the initial permeability increased while the Curie temperature remained almost constant with increasing x. The behavior of coercivity and remanence ratio was discussed. The composition dependence of the dc electrical resistivity is found to support the hopping conduction mechanism.