Structural, AC conductivity and dielectric properties of Sr-La hexaferrite

A series of M-type hexaferrite samples with composition Sr _1-xLa_xFe₁₂O₁₉ (x = 0.00, 0.05, 0.15 and 0.25) were prepared by standard ceramic technique. AC electrical conductivity measurements were carried out at different frequencies (20 Hz-1 MHz) and at different temperatures. The dielectric constant and dielectric loss tangent were measured in the same range of frequencies. The experimental results indicate that AC electrical conductivity increases on increasing the frequency as well as the temperature, indicating magnetic semiconductor behavior of the samples. The increase in AC electrical conductivity with frequency and temperature has been explained on the basis of Koops Model whereas dielectric constant and dielectric loss tangent has been explained with the Maxwell-Wagner type interfacial polarization in agreement with the Koops phenomenological theory.