Electromagnetic noise suppression composite sheets made of hexagonal ferrite particles

Three different compositions of hexagonal ferrites-M-type (SrCo_1.4Ti_1.4Fe_9.2O₁₉), Y-type (Ba₂Zn₂Fe₁₂O₂₂), and Z-type (Ba₃Co_1.25Zn_0.75Fe₂₄O₄₁)-are studied to explore their suitability as an electromagnetic (EM) noise suppressor for 6 GHz band. The metal substitutions are chosen to achieve the largest possible noise suppression capabilities at the desired frequency. Static magnetic characterization reveals excellent soft magnetic properties of Z-type powder with M_S of 51 eμg and H_C of just 8 Oe. However, the high-frequency properties of the Y-type sample are superior to the rest. It possesses the highest μr ′ of 3.8 and noise suppression figure of merit ω × μr ′ ′ (ω) of 23.8 GHz-more than 200% enhancement on the data previously reported by us at 6 GHz. Consequently, the ferrite-epoxy-based composite sheets comprised of 50 vol% of Y-type hexaferrite as magnetic inclusion exhibits the loss ratio, P_Loss/P_In, of 0.21, while the loss ratio of just 0.12 corresponds to more than 10 dB of EM noise suppression. An analytical model based on high frequency structure simulator is created to validate the measured loss ratio and to predict noise suppression capability of any given magnetic sheet.