Strategy-Induced Strong Exchange Interaction for Enhancing High-Temperature Magnetic Loss in High-Entropy Alloy Powders

Abstract

Magnetic loss in high-temperature microwave absorbers typically decreases sharply with rising temperature, limited by the Curie temperature (T_C). Conventional alloys rely on high-proportion additions of magnetic metals to enhance T_C; however, this approach increases electrical conductivity and causes impedance mismatch under high temperatures. In this study, a synergistic strategy for high-entropy alloy (HEA) powders is presented that reduces reliance on high magnetic metal content. This approach involves the formation of magnetic element-rich nanoparticles (MENPs) and the incorporation of the rare-earth element Gd, which effectively stabilizes ferromagnetic ordering at high temperatures. The FeCoCrAlGd_0.2 HEA exhibits a T_C of 947 °C and retains a saturation magnetization of 102 emu g⁻¹ from room temperature up to 700 °C. These intrinsic magnetic properties enable stable magnetic moment precession under high-temperature electromagnetic fields. Notably, the FeCoCrAlGd_0.2 alloy demonstrates significant magnetic loss even at 400 °C. Density functional theory (DFT) calculations indicate that the 3d and 4f electron bands in MENPs are closely aligned in energy levels, inducing strong exchange interactions and thermally stable ferromagnetic ordering in MENPs. This work presents a novel design strategy and research approach for magnetic HEAs, identifying a promising material for high-temperature microwave absorbers.