Construction of chiral magnetic structure with enhancement in magnetic coupling for efficient Low-Frequency microwave absorption.

• The chiral and linear magnetic structure is constructed under the same conditions. • The enhanced magnetic coupling is confirmed by the off-axis electron holography. • The magnetic anisotropy is confirmed by the micro-magnetic simulation. • Superior microwave absorption is achieved by the chiral magnetic structure. Construction of chiral magnetic structure is considered as a promising strategy to achieve efficient low frequency microwave absorption. However, it is not clear that how the magnetic loss is enhanced by the chiral morphology. Herein, a novel chiral magnetic structure containing FeCo 2 O 4 -FeCo nanosheets has been constructed by using helical carbon nanocoils (CNCs) as the chiral template. For comparison, the FeCo 2 O 4 -FeCo nanosheets are also combined with the linear carbon nanofibers (CNFs). The enhanced magnetic coupling between FeCo 2 O 4 -FeCo nanosheets and the magnetic anisotropy induced by the chiral structure are confirmed by the off-axis electron holography and the micro-magnetic simulation. Due to the synergistic effect between chirality, magnetism, and dielectricity, the chiral magnetic structure exhibits superior microwave absorption performance than the linear one with a wide effective bandwidth of 7.1 GHz at an ultra-low filling ratio of 8 %. Meanwhile, the minimum RL value of −60.7 dB is achieved at low frequency (6 GHz). This study provides further evidence of the special mechanisms of the chiral structure for microwave absorption. [ABSTRACT FROM AUTHOR]