Microwave absorption enhancement of FeCoNi contributed by improved crystallinity and flake-like particles

•Fe-Co-Ni alloys with improved crystallinity and flake-like particles are prepared.•The mechanisms for enhanced EM parameters in Ni-substituted samples are revealed.•(FeCo)95Ni5 exhibits broad bandwidth of 7.64 GHz under thin thickness of 1.4 mm. The microwave absorption properties of (FeCo)100−xNix (0 ≤ x ≤ 15) samples were investigated in this study, which were made by a simple single roller melt spinning technique. It was found that the introduction of Ni into FeCo can significantly enhance the crystallinity and flake-like particles in the samples. The complex permeability and permittivity increase gradually with increment of Ni content. Notably, a broad peak emerges in the imagine part of permeability at 4–16 GHz for the Ni-substituted samples which covers almost all the tested frequency region. The contributions of microstructure and morphology to the increased electromagnetic parameters are explored detailedly in this work. Moreover, attenuation ability enhances while impedance matching performance deteriorate gradually with Ni content improving. It is interestingly to find that the sample with x = 5 exhibits the maximum qualified bandwidth (≤−10 dB) of 7.64 GHz with a thin thickness of only 1.4 mm eventually, which is superior to many reported microwave absorbing materials.