Complex permittivity, permeability and wide band microwave absorbing property of La3+ substituted U-type hexaferrite

Polycrystalline samples of U-type hexaferrite series: (Ba1-3xLa2x)(4)Co2Fe36O60 with 0.10 <= x <= 0.20 in step of 0.05, are prepared by conventional solid state reaction route. Partial substitution of Ba2+ ions with La3+ ions enhances the electron hopping and reduces the magnetic interaction in the sample. Relative complex permittivity (epsilon(r) = epsilon' - j epsilon '') and permeability (mu(r) = mu' - j mu '') of the prepared samples were measured using Vector Network Analyzer (VNA, Agilent PNA-L N5230A) for X-band (8.2-12.4 GHz) frequency range. The maximum absorption of 99.8% was obtained for x = 0.10 sample for thickness t(m) = 1.8 mm and all sample showed absorption >= 96%. The reflection loss (R-L) calculated using the measured parameter (epsilon(r) = epsilon' - j epsilon '' and mu(r) = mu' - j mu '') shows good agreement when compared with the return loss measured directly using VNA for sample x = 0.20. The material can be expected to find relevance in suppression of electromagnetic interference (EMI) shielding and reduction of radar signatures. (C) 2010 Elsevier B.V. All rights reserved.