Enhanced electromagnetic wave absorption performance by introducing exchange bias in a CIP@γ-FeOOH heterostructure

Area of Science:

• Materials Science
• Nanotechnology
• Electromagnetics

Background:

• Electromagnetic pollution necessitates high-performance electromagnetic wave (EMW) absorbing materials.
• Conventional carbonyl iron powder (CIP) absorbers exhibit limited absorption bandwidth, especially at low filler concentrations.
• Existing materials struggle to overcome the Snoek's limit for broadband absorption.

Purpose of the Study:

• To design and synthesize a novel hierarchical core-shell absorber based on CIP.
• To enhance the electromagnetic wave absorption performance, particularly bandwidth and reflection loss.
• To investigate the interfacial engineering effects on magnetic loss and polarization mechanisms.

Main Methods:

• A transition-layer-guided oxidation strategy was employed using a sacrificial SiO₂ shell.
• Hierarchical CIP@γ-FeOOH core-shell structures were constructed.
• Characterization of the material's structure, magnetic properties, and electromagnetic wave absorption performance.

Main Results:

• The fabricated CIP@γ-FeOOH absorber exhibited a ferromagnetic/antiferromagnetic (FM/AFM) interface, inducing a significant exchange bias effect.
• This interface enhanced magnetic loss through interfacial pinning and strengthened low-frequency magnetic response.
• The composite achieved a maximum effective absorption bandwidth (EAB_max) of 6.13 GHz (9.38-15.51 GHz) and a minimum reflection loss (RL_min) of -17.68 dB at 60 wt. %.

Conclusions:

• The developed core-shell structure effectively breaks the Snoek's limit constraint for EMW absorbers.
• Interfacial engineering via FM/AFM coupling is a viable strategy for enhancing broadband EMW absorption.
• The findings provide a basis for designing advanced CIP-based absorbers for electromagnetic pollution mitigation.