Yolk–Shell Engineering on Single-Component Fe ₃ O ₄ to Realize Magnetic–Dielectric Synergy for Enhanced Microwave Absorption: Experimental and Simulation Insights

Yolk–shell structural engineering has demonstrated significant advantages in achieving high-performance microwave absorption for multicomponent systems; however, the electromagnetic response mechanism of single-component yolk–shell structure absorbers remain underexplored. This study develops a multistep strategy to fabricate yolk–shell-structured Fe 3 O 4 (YS-Fe 3 O 4 ), which exhibits a substantially broadened effective absorption bandwidth of 6.87 GHz and a RCS reduction value of 40.76 dB m 2, significantly outperforming its solid spherical counterparts (5.39 GHz, 21.1 dB·m 2 ). Experimental results and theoretical simulations reveal that the enhanced microwave absorption originates from the synergistic optimization of dielectric and magnetic loss, which simultaneously improves impedance matching and attenuation capability. Specifically, abundant Fe 3 O 4 /air interfaces and increased oxygen vacancy reinforce the dominance of polarization loss and introduce a supplementary conductive loss at low frequency, thereby strengthening multichannel synergy in dielectric dissipation. Concurrently, the enhanced ferromagnetic resonance contributes to a prominent increase in magnetic loss. In agreement with experiments, molecular dynamics simulations validate the enhancement of polarization-driven dielectric loss, while finite element simulation demonstrates the improved magnetic domain motion and magnetization mechanism. This study provides profound theoretical and computational insights into the electromagnetic response mechanism of yolk–shell structures, offering a valuable guidance for designing high-performance microwave absorbers.