Sparse Nanocrystals Enable Ultra-Low Coercivity and Remarkable Mechanical Robustness in High-Entropy Amorphous Alloy.

Abstract

Ferromagnetic high-entropy alloys (HEAs) are known for their excellent mechanical properties, which are attributed to their abundant ordered structures. However, they often exhibit compromised soft magnetic properties, which restrict their applications in modern electronics. In this study, an order-modulation strategy is introduced to overcome this limitation by constructing an amorphous-nanocrystalline transitional structure in a ferromagnetic HEA system. Subsequently, FeCoNiAlTaSiB high-entropy sparse nanocrystals alloys are developed that possess fine nanocrystals sparsely dispersed in an amorphous matrix. This allows the resultant alloys to combine an ultra-low coercivity (0.3 A m^-1) with remarkable mechanical toughness, achieving a synergistic enhancement of the mechanical robustness and soft magnetic properties. This remarkable mechanical-magnetic synergy is attributed to the presence of numerous crystal-like orders (<2 nm), regular magnetic-domain structures, and minimized magnetic anisotropy. Moreover, the proposed order-modulation strategy successfully extend structural control across the entire order space, from amorphous to crystalline, providing a new paradigm for designing advanced soft magnetic materials with balanced mechanical and magnetic properties.