• A novel multifunctional carbon foam with nanoscale chiral magnetic heterostructures is constructed, in which the interconnection network provides strong conduction loss.
• The interfacial polarization loss induced by the FeNi-carbon interfaces is confirmed by density functional theory calculations, and magnetic pinning and coupling effects are revealed by micromagnetic simulation.
• The composite foam exhibits an ultrabroad effective absorption bandwidth (EAB) of 14 GHz and a C-band EAB of 4 GHz, achieving full C-band coverage.
• This study provides guidelines for designing chiral-dielectric-magnetic trinity composites to achieve broadband microwave absorption in low frequency.