High-performance microwave absorption of Ti/Mn substituted hexaferrite composites in the 6.0–45.5 GHz range

Abstract

This study presents an experimental investigation of Ti/Mn substituted barium hexaferrite composites, positioning them as promising candidates for high-frequency microwave absorption from Ku up to Ka bands (12–40 GHz). The M-type BaTixMnxFe12−2xO19 hexaferrite is obtained by solid-state synthesis. The influence of Ti/Mn substitution (x=0.0–2.0) and particle morphology on the static magnetic and electromagnetic properties (permittivity and permeability spectra) is studied to uncover key relationships for optimizing microwave absorption performance. All elaborated compounds present high electromagnetic losses in Ku and Ka bands. The substituted compound with x=0.4, when mixed with a dielectric matrix at moderate volume concentrations (30% charge), shows a reflection loss of −22.4 dB at 34.60 GHz, a matching thickness of 1.0 mm and an effective reflection loss bandwidth at −10 dB of 9.46 GHz. This elevated effective absorption bandwidth arises from multiple absorption peaks that are present for all synthesized hexaferrites. Micromagnetic simulations combined with an electromagnetic mixing law reproduce the experimental effective permeability spectra and show that the formation of magnetic domains inside each particle is responsible for such multipeak profiles. Supplemental calculations illustrate that it is possible to tune the attenuation performance and frequency window by combining these composites. These results provide insights into how to tune both the chemical composition and the spectral bandwidth of GHz-absorbing hexaferrites.