High-efficiency microwave absorbing performance originating from sufficient magnetic exchange coupling interaction and impressive dielectric loss

Abstract

Exchange-coupled hard–soft magnets have been considered as promising microwave absorbers. However, it is difficult to make further breakthrough in microwave absorption performance due to the deficient dielectric loss. In this work, Cu/Fe₃O₄/BaZr_0.6Ni_0.6Fe_10.8O₁₉ composites with sufficient magnetic exchange coupling interaction and impressive dielectric loss were successfully fabricated. The results show that the crystallinity of Fe₃O₄ enhances gradually by increasing the secondary heat treatment temperature. More spherical Fe₃O₄ particles attach to the surfaces of flake-like BaZr_0.6Ni_0.6Fe_10.8O₁₉ particles from room temperature to 400 °C, increasing the hard/soft magnetic interfaces, while self-aggregation of Fe₃O₄ becomes more pronounced and Cu is oxidized violently to CuO with the further increase of temperature to 600 °C. Eventually, the sample heated at 400 °C shows the strongest attenuation ability due to the common enhancement of magnetic and dielectric loss, and hence exhibits the optimum microwave absorbing performance with a broad absorbing bandwidth of 5.28 GHz at a thin thickness of 2.0 mm.