Novel Polyimide/Copper-Nickel Ferrite Composites with Tunable Magnetic and Dielectric Properties

Heat-resistant magnetic polymer composites were prepared by incorporating cerium-doped copper-nickel ferrite particles, having the general formula Ni_1-xCu_xFe_1.92Ce_0.08O₄ (x: 0.0, 0.3, 0.6, 1.0), into a polyimide matrix. The effects of particle type and concentration on the thermal, magnetic, and electrical properties of the resulting composites were investigated. The samples were characterized by FTIR, scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis, differential scanning calorimetry, vibrating sample magnetometer, and broadband dielectric spectroscopy. The composites exhibited high thermal stability, having initial decomposition temperatures between 495 and 509 °C. Saturation magnetization (M), magnetic remanence (M), and coercivity (H) were found in range of 2.37-10.90 emu g^-1, 0.45-2.84 emu g^-1, and 32-244 Oe, respectively. The study of dielectric properties revealed dielectric constant values of 3.0-4.3 and low dielectric losses of 0.016-0.197 at room temperature and a frequency of 1 Hz.