Barium Ferrite with High Anisotropy for Ultra‐Broadband Microwave Absorption

Abstract In the 5G era, Barium ferrite (BaFe 12 O 19 ) has a pivotal position in both fundamental research and frontier applications, such as magnetic recording, microwave absorption, and 2D spintronic devices. Currently, BaFe 12 O 19 is hard to achieve a desirable broadband microwave absorption (MA) because of the underutilized magnetic property limited by Snoek limit, though some efforts have been made by improving the dielectric property to enhance microwave attenuation. The structural design of high anisotropy is deemed an efficient strategy to break the intrinsic Snoek limit of BaFe 12 O 19 . The high‐anisotropy 2D nanosheets and 1D nanotubes via ordered growth and assembly can elevate magnetic properties and resonance response. Such optimized spatial structure arrangement can realize ultrawide effective absorption bandwidth (EAB) up to 8.7 and 3.0 GHz, respectively, superior to 0 GHz for conventional BaFe 12 O 19 powders. The morphologies and microstructures of BaFe 12 O 19 effectively trigger shape and magnetic anisotropy, which not only breaks the intrinsic Snoek limit to induce magnetic loss‐dominated MA mechanism, but also promotes dielectric‐magnetic cooperative loss via improved magnetoelectric mutual inductance effect in 1D/2D structures. These results allow for the management of magnetic properties and controllable structural designs of BaFe 12 O 19 , providing a reliable means toward ultra‐convenient preparation of high‐anisotropy magnetic materials for more frontier applications.