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MM: Fachverband Metall- und Materialphysik

MM 53: Structural Materials (Steels, light-weight materials, high-temperature materials) - II

MM 53.6: Vortrag

Donnerstag, 19. März 2020, 13:00–13:15, BAR 205

Impact of paramagnetism on grain boundary energetics in FeMn — •Omkar Hegde, Tilmann Hickel, Christoph Freysoldt, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany

To understand the impact of the magnetic disorder on defect energetics and kinetics is, though conceptually and computationally challenging, important for designing Fe-based alloys. Since magnetic degrees of freedom change faster than atomic degrees of freedom in the high-temperature paramagnetic state, the atoms move according to an averaged force instead of instantaneous forces attained from each spin configuration.

Therefore, a new computationally efficient method based on spin-space averaging [1] (SSA) has been developed to handle magnetic disorder next to defects. First, we focus on the vacancies in FeMn system, for which we demonstrate that paramagnetism significantly affects atomic relaxations as well as diffusion barriers and thereby we explain why Mn diffusion shows a different temperature dependence than Fe-self diffusion in α-Fe. Next, we expand our method to extended defects and present the impact of paramagnetism on the grain boundary energetics of Mn in FeMn. Finally, we combine our results to propose a pathway for Mn segregation to grain boundaries.

[1] F Körmann, A Dick, B Grabowski, T Hickel, and J Neugebauer, Phys. Rev. B 85(12):125104, (2012).