Hard-Soft Magnetic Composite as Microwave Absorber in S-Band and C-Band

This research discusses synthesizing and characterizing magnetic hard-soft composite materials (Ba 0.6 Sr 0.4 Fe 11.5 Al 0.5 O 19 /NiFe 2 O 4 ) applied as microwave absorbers at S-band and C-band frequencies. The mechanical alloying method for sample synthesis uses a high-energy ball mill and sintering at high temperatures. Characterization of the crystal structure was done using an X-ray diffractometer. The Ba 0.6 Sr 0.4 Fe 11.5 Al 0.5 O 19 sample (hard magnetic) has a hexagonal structure, while the NiFe 2 O 4 (soft magnetic) has a cubic structure. SEM analysis revealed a heterogeneous form with particle sizes ranging from 0.4 to 0.8 µm. Magnetization at room temperature was characterized using a vibrating-sample magnetometer (VSM). The magnetization saturation (Ms), magnetic remanent (Mr), and field coercivity (Hc) are 54.22 emu/g, 21.68 emu/g, and 0.876 kOe, respectively. Microwave absorption characterized using vector network analysis (VNA) shows that the hard-soft magnetic composite sample (Ba 0.6 Sr 0.4 Fe 11.5 Al 0.5 O 19 /NiFe 2 O 4 ) has a minimum reflection loss (RLmin) value of -29.86 dB for the S-band and -18.76 dB for the C-band area with an effective bandwidth reaching 2.34 GHz.