Improvement of soft magnetic properties for Fe-based amorphous/nanocrystalline alloy by longitudinal magnetic field annealing

Abstract

• longitudinal magnetic field annealing (FA) and co synergistically affect the microstructure, magnetic domain behavior, and soft magnetic properties of Fe-based amorphous/nanocrystalline alloy. • FA promotes fine nanocrystalline nucleation and suppresses grain growth from amorphous matrix. • FA improves the soft magnetic properties of Fe-based amorphous/nanocrystalline alloy. • Co 16 achieves the best comprehensive soft magnetic properties with b s of 1.85 T, low h c of 1.8 A/m, and exceptional μ e of 26,505 at 1 kHz. This study investigated the enhancement of soft magnetic properties in Fe 83.2-x Co x Si 2.5 B 9.5 P 4 Cu 0.8 ( x = 0, 4, 8, 12 and 16 at %) amorphous/nanocrystalline alloys through longitudinal magnetic field annealing (FA). The FA-treated alloys demonstrate superior magnetic performance, achieving a superior saturation flux density ( B s ) of 1.85 T, ultra-low coercivity ( H c ) of 1.8 A/m, high effective permeability ( μ e ) of 26,505 at 1 kHz, and low core loss (0.13 W/kg) at 1.0 T/50 Hz. Microstructural analysis reveals that the FA and Co substitution promotes nanocrystalline nucleation, forming high-density nanocrystals while suppressing grain growth through competitive dynamics and inhibiting element diffusion within the amorphous matrix. Domain observation further confirms that FA facilitates the transition from disordered, non-uniform magnetic to uniform, broad, plate-like domains. These findings elucidate the critical influence of longitudinal magnetic field annealing on microstructure evolution and magnetic domain alignment, which synergistically enhance soft magnetic properties.