Tuning of microwave absorptive behavior of double substituted barium hexaferrites with change in thickness in 26.5-40.0 GHz band

Double substituted M-type barium hexaferrites were synthesized using conventional solid state reaction method. Vector Network Analyzer was used to analyze the microwave absorption properties of synthesized hexaferrites. The complex permittivity and complex permeability of the composite samples have been measured in Ka-band (26.5-40.0 GHz) frequency range. The dielectric constant (epsilon') of all the samples lies in the range 4.2-7.5 and decreases with the substitution of impurity ions. The values of the dielectric loss (epsilon '') spectra are almost flat in complete frequency band for the doped samples (x = 0.05-0.25), which lies in the range 0.25-2.25. The permeability (mu') decreases with frequency for the doped samples and lies between 0.85 and 1.4. The magnetic loss (mu '') spectra for the doped samples x = 0.05-0.25 register a loss between 0.00 and 0.21 in whole frequency band. The prepared samples can absorb more than 99% of microwave signal at specific frequencies in the Ka-band. The sample with composition Ba0.8La0.15Na0.15Fe10CoZrO19 shows reflection loss (RL) = -47.55 dB at thickness 3.0 mm with -10 dB bandwidth of 5.13 GHz, while shows RL -25.29 dB with -10 dB bandwidth of 6.75 GHz at thickness 2.6 mm. The results show that with the change in absorber thickness, there is a shift in matching frequency. The material is expected to find relevance in reduction of radar signatures and electro-magnetic interference suppression.