Complex permittivity, permeability and wide band microwave absorbing property of La 3+ substituted U-type hexaferrite

Abstract

Polycrystalline samples of U-type hexaferrite series: (Ba 1−3 x La 2 x ) 4Co 2Fe 36O 60 with 0.10≤ x≤0.20 in step of 0.05, are prepared by conventional solid state reaction route. Partial substitution of Ba 2+ ions with La 3+ ions enhances the electron hopping and reduces the magnetic interaction in the samples over the entire X-band frequencies; leading to wide band microwave absorption in all sample. Relative complex permittivity ( ε r = ε′− jε″) and permeability ( μ r = μ′− jμ″) 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 (ε r = ε′− jε″ and μ r = μ′− jμ″) 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.