Excellent NiO–Ni Nanoplate Microwave Absorber via Pinning Effect of Antiferromagnetic–Ferromagnetic Interface

Materials with strong magnetic property that can provide excellent microwave absorption performance are highly desirable, especially if their dielectric and magnetic properties can be easily modulated, which make minimal thickness and ultrawide bandwidth become achievable. The magnetic properties of ferromagnetic (FM) and antiferromagnetic (AFM) composite materials are closely related to their ratio of composition, size, morphology, and structure. AFM–FM composites have become a popular alternative for microwave absorption; however, the controllable design and preparation need to be urgently optimized. Here, we have successfully prepared a series of platelike NiO–Ni composites and demonstrated the potential of such composites for microwave absorption. Strong magnetic coupling was found from NiO–Ni nanoparticles by electron holography, which makes NiO–Ni composites a highly efficient microwave absorber (strong reflection loss: −61.5 dB and broad bandwidth: 11.2 GHz, reflection loss < −10 dB). Our findings are helpful to develop a strong microwave absorber based on magnetic coupling.