SKM 2021 – scientific programme

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MA: Fachverband Magnetismus

MA 15: Posters Magnetism IV

MA 15.35: Poster

Thursday, September 30, 2021, 13:30–16:30, P

Effect of chemical disorder on the magnetic exchange couplings in L1₀ FeNi (tetrataenite) — •Ankit Izardar and Claude Ederer — Materials Theory, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland

L1₀ Fe₅₀Ni₅₀ (tetrataenite) is a promising candidate for permanent magnets with relatively high energy product containing only cheap and abundant elements. Unfortunately, the laboratory synthesis of the ordered phase is extremely challenging and several attempts have been made to achieve a high degree of chemical order in this alloy. Therefore, it is important to know how deviations from perfect chemical order affect magnetic properties.

Using first-principles-based density-functional theory calculations, we provide insights into the impact of the chemical disorder on the magnetic exchange interactions in tetrataenite. Our calculations show very strong variations in the magnetic exchange couplings (by more than 80%). Furthermore, by employing a model study, we estimate the effect of these strong variations in, e.g., the nearest neighbour couplings, compared to simply using averaged coupling constants. Our results indicate that using averaged coupling constants can lead to an overestimation of the Curie temperature of around 5%.