Correlating the coating cycles, integrity and magnetic properties of Fe–Ni–Mo soft magnetic composites by a powder atomic layer deposition method

Abstract

Coatings play a crucial role in minimizing eddy current loss in soft magnetic composites (SMCs). The powder atomic layer deposition (PALD) technique was utilized to coat Fe–Ni–Mo soft magnetic powder in this study. The Al2O3 coating fabricated via PALD enhanced corrosion resistance and reduced core loss in SMCs. Additional deposition cycles increased the resistivity of the Fe–Ni–Mo powder and the corrosion resistance of the Fe–Ni–Mo SMCs, indicating that the density and integrity of the amorphous Al2O3 coating were enhanced. Thinner coatings (20 cycles) exhibited anodic passivation in corrosion, which was attributed to insufficient density. Nevertheless, an excessively thick coating (100 cycles) resulted in a decrease in effective permeability and an increase in hysteresis loss. The fabricated Fe–Ni–Mo SMCs (50 cycles) demonstrated a core loss of 603.1 mW/cm3 at 100 kHz/100 mT, coupled with an effective permeability of 108.5 and a Q value of 97.8 at 100 kHz.