Overcoming the Trade‐Off Between Magnetic Coupling and Electrical Insulation in Soft Magnetic Materials via Nanochain Engineering

Abstract The development of high‐frequency soft magnetic materials (HFSMMs) that simultaneously achieve high saturation magnetization strength ( M s ) and high electrical resistivity ( ρ ) represents a significant challenge, primarily due to the inherent trade‐off between magnetic coupling and electrical insulation. Herein, a novel approach is presented to address this challenge through the self‐isolated Fe/FeCo nanochains with continuous oxide encapsulation, fabricated via a magnetic field‐assisted chemical synthesis combined with in situ oxidation. The unique nanochain architecture facilitates robust magnetic coupling between nanoparticles, while an ultrathin oxide layer (≈10 nm) provides effective electrical isolation, enhancing resistivity. Detailed structural and theoretical analyses demonstrate that the amorphous‐crystalline interfaces promote spin polarization through charge recombination, thereby boosting magnetization, while the metal‐oxide interfaces confine eddy currents within individual nanoparticles, significantly reducing high‐frequency core losses. The resulting nanochain soft magnetic composites (nanochain‐SMCs) exhibit an exceptional property: Fe nanochains achieve M s = 149.2 emu g −1 and ρ = 0.86 Ω·m, while FeCo nanochains reach M s = 172.1 emu g −1 and ρ = 0.41 Ω·m, alongside outstanding frequency stability. This study highlights the synergy between magnetic and charge dynamics in low‐dimensional materials, providing a new insight for the development of HFSMMs.