Determining the preferable polarization loss for magnetoelectric microwave absorbers by strategy of controllably regulating defects

[Display omitted] •The preferable polarization loss for Fe/C/N hybrid was explored by defects engineering.•The proportion of polarization and conductive loss has been identified quantitatively.•The g-C3N4/Fe3C with dominant polarization loss shows the optimal absorption property. Regulating the inner defects could lead to transformation of the prominent dielectric loss for the microwave absorbers, which is a necessary foundation to explore the preference type of dielectric loss mechanism. Herein, in this work, selective molar ratios of melamine/cetyl trimethyl ammonium bromide (CTAB) precursors were designed to construct the Fe/C/N based hybrid materials. The results demonstrate that the dominated polarization loss can be obtained with the high molar ratio of melamine/CTAB due to the improved level of defects density such as point defects, heterointerface distortion, etc. Differently, it is easy to obtain the conductive carbon phase and high crystallinity degree of Fe3C with a low melamine/CTAB molar ratio, achieving significantly conductive loss. Finally, the Fe/C/N hybrid with dominant polarization loss harvests a broad bandwidth of 6.2 GHz at 1.7 mm, verifying the superiority of polarization loss for enhancing electromagnetic absorption performance. Furthermore, simulation results prove that this composite possesses the desirable radar cross section (RCS) reduction and electromagnetic protection for the human head, indicating the potential applications in both military and civilian fields.