Broad-band microwave absorption of Sr0.85La0.15(MnZr)xFe12-2xO19 hexagonal ferrite in 18-40 GHz frequency range

In this research, electro-magnetic (EM) absorption was investigated for M-type strontium hexaferrite with chemical composition, Sr0.85La0.15(MnZr)(x)Fe12-2xO19 (x = 0, 0.25, 0.50, 0.75, 1.0) at microwave frequencies. Complex permittivity (epsilon '-epsilon '') and complex permeability (mu '-mu '') was measured using transmission and reflection (T/R) based waveguide method in the K-band (18-26.5 GHz) and Ka-band (26.5-40 GHz) frequency range. The variation of reflection loss (RL) with sample thickness, frequency and substitution has been analyzed. The matching thickness of the synthesized ferrite was successfully predicted from quarter-wavelength (lambda/4) mechanism which helps to optimize the minimum reflection Nloss (RL) in the material. In K-band, the minimum reflection loss (RL) of -47.8 dB was obtained for composition x = 1.0 with -10 dB (90%) bandwidth of 7.97 GHz and -20 dB (99%) bandwidth of 5.6 GHz at sample thickness 1.1 mm. In Ka-band, the maximum absorption with minimum RL of -29.9 dB with -10 dB bandwidth of 8.72 GHz was obtained for composition x = 0.50 at 0.85 mm sample thickness. These synthesized ferrites find application as thin sheet of microwave absorber with broad bandwidth for EMI (electromagnetic interference) shielding and radar camouflaging. (C) 2018 Elsevier B.V. All rights reserved.