Complex Permittivity and Permeability of Low-Temperature Sintered M-Type Barium Hexaferrite in Ka-Band Frequency Range

The magnetic permeability and dielectric permittivity of M-type barium hexaferrites (BaM) sintered at 920 °C with different additive amount of Bi 2 O 3 are studied in Ka-band frequencies (26.5 ~ 40 GHz). The permeability and permittivity spectra of these low-temperature sintered BaM are determined for the first time in the millimeter-wave range due to their potential application in various millimeter-wave devices. The phases, microstructures and density have been also analyzed. The results show that there is not much difference in the permeability values, but the dielectric constant e' is improved from ~9 to ~18, with the increasing Bi 2 O 3 amount from 0 to 5 wt%. Besides, much lower dielectric loss can be obtained with Bi 2 O 3 content in the range of 2-3 wt%. These low-temperature sintered BaM exhibit lower dielectric loss at Ka-band frequencies compared with that sintered at high temperature.