Probing element-specific magnetism in Ga-and Ge-containing CoMnFeNi high-entropy alloys by XMCD

High-entropy alloys (HEAs), multicomponent systems stabilized by chemical disorder and configurational entropy, provide a versatile platform to study the interplay of FM and AFM interactions. We synthesized nanocrystalline CoMnFeNi, CoMnFeNiGa and CoMnFeNiGe bulk HEAs by spark plasma sintering (SPS) and observed pronounced differences in structure and magnetism. Addition of Ga and Ge to the CoFeNiMn leads to FC →BCC phase transformation and an enhancement of Ms and Tc. To disentangle the role of individual elements, we would like to exploit hard X-rays MCD at the ERSF, enabling element-specific probing of 3d metals and sp-elements (Ga and Ge) across temperature and field regimes. Combination of XMCD, macroscopic magnetization (M), and complementary atom probe tomography should uncover a link between local M and atomic-scale chemical distributions. This approach clarifies how Ga/Ge alloying and crystallinity control exchange interactions and stabilize unusual magnetic states in HEAs.