Improvement of absorption performance for Co2Z barium ferrite composite by increasing the reflected electromagnetic wave from air–absorber interface

•The permittivity of the Co2Z barium ferrite composite was enhanced by adding the graphite powder into the composite.•The higher permittivity leads to the enhanced electromagnetic wave energy reflected from air–absorber interface.•The enhanced electromagnetic wave energy reflected from air–absorber interface results in strong absorption peaks.•The origin of the RL enhancement was deeply investigated.

Co2Z barium ferrite composite with the added graphite powder was prepared to increase the permittivity. The calculated results showed that the stronger reflection loss (RL) peak and the smaller absorber thickness were simultaneously achieved compared with the pure Co2Z barium ferrite composite with the same permeability but lower permittivity. The origin of the absorption peaks was discussed by quarter-wavelength cancellation. By measuring the reflection coefficient of the composites without (S11-OPEN) and with (S11-SHORT) a backed metal plate, the separated electromagnetic wave energy reflected at the air–absorber interface and the absorber–metal plate interface was achieved, and they were used to deeply investigate the reason of the RL enhancement.