Frequency tunable Ni-Ti-substituted Ba-M hexaferrite for efficient electromagnetic wave absorption in 8.2-75 GHz range

The development of 5G telecommunication technology has seen a high demand for effective electromagnetic (EM) wave absorbers in the millimeter wave (mmWave) band. Because hexagonal M-type ferrite is known to have high ferromagnetic resonance (FMR) in the 5G band frequency, it has attracted significant attention as a mmWave absorber. However, study of the relationship between magnetocrystalline anisotropy, FMR frequency, and EM wave absorption performance in the mmWave band remains insufficient. In this study, Ni-Ti-substituted M-type barium ferrite (Ba-M ferrite) was synthesized using the citrate sol-gel method, and the change in the magnetic properties caused by Ni-Ti substitution was analyzed. The complex permittivity, permeability, and reflection loss (RL) of the Ni-Ti-substituted Ba-M ferrite composites in the 8.2-75 GHz broadband frequency range were also studied. The EM wave absorption frequency, which is governed by the FMR frequency, could be tuned by controlling the amount of substituted Ni-Ti ions in the Ba-M ferrite. The prepared EM wave absorber exhibited excellent EM wave absorption properties with an RL of -52 dB at 29.5 GHz and a matching thickness of 0.95 mm. This study provides insights into a frequency-tunable EM wave absorber with enhanced absorption properties, attained by changing the magnetic properties of Ni-Ti-substituted M-type hexaferrites in the mmWave frequency band.