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

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: Ba4Co2−xMnxFe36O60, 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 RL = −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.