Plasma‐Assisted Engineering of Fe–Si–Al/AlN Soft Magnetic Composites for Concurrent Magnetic Loss Reduction and Thermal Transport Enhancement

Conventional soft magnetic composite fabrication typically addresses either the insulating phase or powder morphology in isolation, limiting comprehensive performance optimisation. Here, we propose a bulk–phase coupled strategy in which plasma‐assisted ball milling simultaneously transforms spherical Fe–Si–Al powder into a lamellar structure and coats it with an AlN insulating layer. The lamellar morphology, via shape anisotropy, extends the upper frequency limit of permeability, while the AlN layer suppresses eddy currents and facilitates heat dissipation. At an optimised discharge power of 1300 W, the composite delivers a total loss of 178.3 kW·m −3 (10 mT, 500 kHz) and a thermal conductivity of 20.2 W·m −1 ·K −1 , corresponding to a ∼ 68°C reduction in steady‐state operating temperature relative to uncoated Fe–Si–Al under simulated conditions. These results establish plasma‐assisted bulk–phase engineering as a generalisable route towards high‐frequency, low‐loss soft magnetic composites with integrated thermal management capability.