We prepared a high-quality magnetic BaCoTiFe 10 O 19 ferrite-based composite sheet and BaCoTiFe 10 O 19 thin films exhibiting in-plane magnetic anisotropy. In-plane magnetic anisotropy was realized by controlling particle orientation to achieve high-resonance frequency values. The dynamic permeability of the samples in the GHz-frequency region was evaluated by the short-circuited microstripline method up to 30 GHz. Controlling the propagation of electromagnetic waves with GHz frequencies is extremely difficult. Nevertheless, the ferromagnetic resonance phenomena were observed, and the obtained sheet showed a resonance frequency value of approximately 4 GHz. However, the intrinsic ferromagnetic resonance behaviors were not elucidated for the thin films. The obtained BaCoTiFe 10 O 19 powder/ polymer composite sheet and BaCoTiFe 10 O 19 thin films may have the potential for use at GHz frequencies and as anisotropicelectromagnetic wave suppression materials.