Regensburg 2019 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 12: Poster session I

MM 12.11: Poster

Montag, 1. April 2019, 19:15–20:45, Poster C

Ab-initio Phase Stabilities of Ce-based Hard Magnetic Materials — •Halil ibrahim Sözen, Tilmann Hickel, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany

Due to the developments in e-mobility and renewable energies, hard magnets composed of rare earths have gained increasing importance in the last decades. Recently, there is a growing interest in developing alternative hard magnetic materials, that reduce or even remove the need to use their expensive RE elements. The strategy is to use 3d elements with high magnetic anisotropy such as e.g. Fe-Co-B alloys. In order to support these efforts, we performed ab initio calculations of finite temperature phase stabilities of Ce-based alloys. The Helmholtz free energy F(T, V) is calculated for all relevant competing phases using a sophisticated set of methods capturing vibrational, electronic, magnetic and configurational entropy contributions. The study includes unary Ce, binaries of Ce-Fe and Fe-Ti phases, and ternary Ce-Fe-Ti phases. In a first step, we test the performance of our approach and find good agreement with experimental data. In a second step, we calculate the finite temperature phase formation diagram. This diagram shows that the presence of the CeFe2 phase prevents any formation of the targeted hard magnetic Ce-Fe-Ti alloys. This observation is supported by recent EDS experiments. In a third step, we, therefore, extend our study to quaternary alloys. Specifically, we study the effects of Cu and Ga substitution by introducing a screening scheme that allows testing all 3d and 4d elements.