Dual‐phase CoFe 2 S 4 /CoFe 2 O 4 nanoflowers with multiple interfacial polarization responses for superior electromagnetic wave absorption

Abstract Transition metal sulfides and oxides with suitable dielectric features have been considered as significant candidates for advanced electromagnetic wave (EMW) absorption systems. However, there is still an urgent need to realize controllable regulation of their interfacial polarization behavior. Herein, we prepared dual‐phase CoFe 2 S 4 /CoFe 2 O 4 composites with an average size of ~ 1.43 μm through a hydrothermal method. The unique nanoflower morphology promoted the multiple reflection and scattering of the incident EMW, contributing to the improvement of the loss ability. By varying the temperature during the solvothermal reaction, a facile adjustment of the CoFe 2 O 4 to CoFe 2 S 4 ratio can be realized. The difference in electronegativity and band gap facilitated the directional electron transfer from CoFe 2 O 4 side to CoFe 2 S 4 side at the dual‐phase heterogenous interfaces, leading to spatial charge redistribution and optimized in‐plane interfacial polarization. Moreover, the different distribution of CoFe 2 O 4 and CoFe 2 S 4 phases on different nanosheets exaggerated the deviation of interlayer positive/negative charges from the original equilibrium centers, thereby contributing to the enhancement of interlayer polarization. As a result, CoFe 2 S 4 /CoFe 2 O 4 with higher dual‐phase density exhibited strongest absorption intensity of −77.2 dB with an effective absorption bandwidth of 7.2 GHz at 1.8 mm. This work demonstrates the effective EMW attenuation optimization in transition metal sulfides and oxides and paves the way for modulating multiple interfacial polarization responses in inhomogeneous absorber systems.