The RE-ST-FE and RE-BT-FE/FR composites have been prepared and characterized using time domain spectroscopy method in the [DC-12.5] GHz range. The dielectric, magnetic, and electrical properties of the ternary composites have been investigated. In the RE-ST-FE composite, the dielectric permittivity (ε’) has been found to decrease from 9.25 to 3.70 with increase in FE concentration. While it has been observed that the electrical conductivity increases as the ST concentration increases reaching a value of 11.6 (mS / m) and shows a percolation behavior with (Vth = 26,9% ST). In the RE-BT-FE/FR composites, the magnetization hysteresis loops have been measured by vibrating sample magnetometer from -3 to +3 kOe. This has made it possible to have a maximum of saturation magnetization equal 29.3 emu/g and the permeability value close to 1.9 with the RE-BT-FR composite which is considered higher than that of the other one. It was found that an increase in the (FE/FR) concentration increases the magnetic permeability, which is confirmed by the modified Lichtenecker law with error ratio less than 0.5%. The results of this study will undoubtedly yield new materials that can be used to miniaturize electronic components used in telecommunications systems, resonators, antennas and wave absorbers.