Overcoming the Trade-Off Between Magnetic Coupling and Electrical Insulation in Soft Magnetic Materials via Nanochain...

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.