Nickel–zinc ferrite–epoxy composites withdifferent ferrite/epoxy ratios, 50/50, 60/40, 70/30 and 80/20, have been
prepared as thick ﬁlms of thickness 100 mm. Different compositions of nickel–zinc ferrite, Ni10xZnxFe2O4, where x ¼ 0:2; 0:4 and 0.5 have been used to prepare the composite ﬁlms. The complex permittivity (e0 - je00) and the complex permeability (m0 - jm00) of the ﬁlms as well as of the sintered ferrites have been measured at X-band (8-12 GHz) microwave frequencies using the cavity perturbation technique. The dielectric constant and the permeability of the ﬁlms are found to be different from those of the sintered ferrites. e0 of ﬁlms is found to increase withincrease in the ferrite content of the composites as well as with frequency while the permeability, m0; is observed to decrease withincrease in ferrite content as well as frequency. The high permeability losses exhibited by the ﬁlms at X-band frequencies, shows their potentiality for applications like suppression of electromagnetic interference in microwave circuits. The composites withth e ferrite composition x ¼ 0:5 are observed to exhibit higher losses compared to the composites with other compositions. Also the ferrite/epoxy ratio 80/20 is observed to give comparatively higher losses.