Electrical, Magnetic and Microwave Absorption Properties of M-type Barium Hexaferrites (BaFe_12-2x Co_xNi_xO₁₉)

M-type barium hexaferrites synthesis with Co-Ni doping ion (BaFe_12-2x Co_xNi_xO₁₉) based on natural iron sand of Loang Balok beach, Lombok, Indonesia, to be applied as a microwave absorbent material using co-precipitation method. The materials used in the synthesis process are magnetite minerals (Fe₂O₃ and Fe₃O₄), 12M HCl, NH₄OH 37%, CoCl₂.6H₂O and NiCl₂.6H₂O. This research to investigate the effect of doping ion concentration variation (x = 0.0, 0.6 and 1.0) and calcination temperature (T = 80, 600, and 800°C) on electrical and magnetic properties and microwave absorption as well. The samples were characterized using Vibrating Sample Magnetometer (VSM) and Network Vector Analyzer (VNA). The result from VSM showed that the coercivity value decreased when doping ion concentration and calcination temperature increased (0.151 Tesla at 600°C for x = 0.0 and 0.044 Tesla at 800°C for x = 1.0. The value of magnetic saturation and the magnetic remanence increased with increasing ion concentration (Ms = 0.327 emu/g at x = 0.0 increased to 35.4 emu/g at x = 1.0) and Mr = 0.148 emu/g for x = 0.0 increased to 15.6 emu/g at x=1.0, this indicates that the sample has been soft magnetic. The result from VNA showed that the electrical conductivity values measured in the range 8.0-15.0 GHz indicate that the sample is a semiconductor (6.149 x 10^-6 -5.975 x 10^-4 S/cm). It also showed that the microwave absorption properties increased at higher concentration of doping ions and the calcination temperature would increase the value of Reflection Loss (RL). The maximum RL value of the sample is -14.47 dB at 12.38 GHz, and the absorption coefficient of 96.43%. These results indicate that the BaFe_12-2x Co_xNi_xO₁₉ sample can be applied as a microwave absorbent material on X-band to Ku-band frequency.