Abnormal dielectric behaviour in polycrystalline zinc-substituted manganese ferrites at high frequencies

Dielectric constant (epsilon'), dielectric loss tangent (tan delta) and complex dielectric constant (epsilon") have been measured for the samples of the type Mn1-xZnxFe2O4 (x = 0.3, 0.5, 0.7 and 0.9). The measurements were carried out in the high frequency range of 100 kHz-1 MHz. The dielectric behaviour is found to be abnormal, giving a peak at a certain frequency. The peak shifts to lower frequency due to increasing zinc concentration. The variation of dielectric behaviour with composition, frequency and temperature is explained qualitatively. The dielectric constant for these mixed ferrites is approximately inversely proportional to the square root of the resistivity. An attempt is made to explain the possible mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.