Enhanced microwave absorption using multiple heterostructures derived from in-situ grown Sn-metal-organic framework on La-doped Fe3O4

As a representative magnetic oxide absorber, Fe 3 O 4 has attracted considerable research attention owing to its remarkable magnetic saturation strength as well as semiconducting properties. Doping Fe 3 O 4 with La 3+ leads to 3d-4f magnetic coupling and ion distribution changes due to the unique electron configuration and large ionic radius of La 3+ , thereby greatly enhancing the magnetic performance. However, high density, low dielectric loss, and low permeability at high frequencies inhibit the electromagnetic wave absorption (EMWA) performance of ferrites. In this study, stick-shaped Sn metal-organic framework (MOF) is in-situ grown on La 3+ -doped Fe 3 O 4 using a surfactant. After high-temperature annealing, the SnO 2 /porous carbon composites derived from Sn-MOF wrap the ferrite, forming a core-shell heterostructure, which not only prevents oxidation but also enhances the EMWA performance. Among the prepared La x Fe 3-x O 4 /SnO 2 /C (LFSC) samples, LFSC-2 (with La x Fe 3-x O 4 to Sn-MOF ratio of 1:2) exhibits strong absorption performance with a minimum reflection loss ( RL min ) of −44.1 dB. Furthermore, the gradient metamaterial based on LFSC-3 shows ultra-broadband EMWA with an effective absorption bandwidth ( RL min  ≤ −10 dB) of 13.17 GHz. In addition, the LFSC-2 sample demonstrates excellent radar stealth capability in the radar cross section (RCS) far-field response, achieving an RCS reduction value of 20.4 dB∙m 2 .