Complex permittivity, permeability and microwave absorbing studies of (Co2−xMnx) U-type hexaferrite for X-band (8.2–12.4GHz) frequencies

Abstract

In order to develop a new microwave absorbing material over the X-band (8.2–12.4 GHz) frequency range, polycrystalline samples of U-type hexaferrite series: Ba 4 Co 2− x Mn x Fe 36 O 60 , with x varying from 0 to 2.0 in steps of 0.5, were prepared through conventional solid state reaction route. X-ray diffraction analysis was done to find the structural change with composition. The variation of electromagnetic parameters (complex permittivity ɛ * = ɛ ′ − jɛ ′′ and complex permeability μ * = μ ′ − jμ ′′) and microwave absorbing properties were studied over the X-band frequency range with varying composition. Both dielectric loss ( ɛ ′′) and magnetic loss ( μ ′′) were found to decrease with increasing x , whereas the dielectric constant ( ɛ ′) and magnetic permeability ( μ ′) variations are reciprocal with Mn addition. Composition with x = 1, presenting a maximum value of microwave absorption of 99.84% (or reflection loss R L = −28.4 dB) at 8.45 GHz when sample thickness is 1.7 mm. This composition also offered wide band absorption (>96%) throughout the X-band frequencies where it can be used for suppressing electromagnetic interference and radar signature.