Dresden 2026 – scientific programme

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MA: Fachverband Magnetismus

MA 22: Focus Session: Materials Discovery II – High throughput searches for functional magnetic materials (joint session FM/MA)

MA 22.4: Talk

Tuesday, March 10, 2026, 15:00–15:15, BEY/0138

Ab initio-based phase diagrams for compositionally complex ThMn12-type alloys — •Sourabh Kumar¹, Semih Ener², and Tilmann Hickel¹ — ¹Bundesanstalt für Materialforschung und -prüfung, 12489 Berlin — ²Technische Universität Darmstadt, 64289 Darmstadt

The structural and chemical stability of rare-earth-based transition-metal (such as Nb, Ce, and Sm) alloys is critical in determining the performance of modern hard magnets (HMs), particularly their coercivity and thermal robustness. This study examines the intrinsic phase competition in (Sm/Ce)-(Fe/Co)-Ti systems, focusing on how Ti additions influence the thermodynamic stability of high-temperature HMs. Two compositional pathways were examined: one dominated by Sm/Ce-Fe/Co binary chemistry and the other influenced by (Sm/Ce)-(Fe/Co)-Ti ternary interactions. We employed ab initio calculations to investigate the finite-temperature stability of ordered, disordered, and metastable phases, thereby guiding experiments. Based on the computed energetics, we analyzed how Ti incorporation alters local bonding environments and stabilizes magnetically desirable motifs. Furthermore, we constructed an ab initio phase diagram to reveal the interplay between rare-earth metals and transition metals across a broad temperature range. We have revealed that Ti addition promotes the formation of a more robust Sm-rich phase by strengthening the local Sm-Fe-Ti matrix. This stabilization enhances alloy coercivity and provides insights into the thermodynamic and chemical factors driving phase evolution, enabling the design of better permanent HMs.

Keywords: Hard Magnets; Ab Initio Methods; Phase Diagrams; Rare-earth metal alloys; Thermodynamics