Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 66: Poster 3

MA 66.15: Poster

Freitag, 24. März 2017, 09:30–13:00, P2-OG2

Isotropic, high coercive field in melt-spun tetragonal Heusler Mn₃Ge — •Adel Kalache¹, Susanne Selle², Guido Kreiner¹, Gerhard H. Fecher¹, Thomas Höche², and Claudia Felser¹ — ¹Max Planck Institut CPFS, Dresden, Germany — ²Fraunhofer Institute for Microstructure of Materials and Systems IMWS, Halle, Germany

Tetragonally distorted Heusler are known for their high crystalline anisotropy, tunable magnetization and high Curie temperature and therefore are candidates for rare-earth-free permanent magnets. We report on nanostructured Mn₃Ge ribbons with a composition ranging from 77 to 74 at.% Mn prepared using induction melting, melt-spinning and subsequent heat treatment. Obtained ribbons show hard magnetic properties due to the highly anisotropic tetragonal D0₂₂ structure of Mn₃Ge. Depending on the composition and the amount of ferrimagnetic Mn₅Ge₂ as a secondary phase, a coercivity of up to µ₀H_C = 2.62 T was obtained for the Mn₇₅Ge₂₅ composition. Microstructure investigations by transmission electron microscopy confirmed the formation of the secondary phase. All samples show isotropic coercive fields, i.e. independent of the direction of the applied magnetic field in contrast to already known epitaxial thin films. The Curie temperature was found to be higher than 800 K, which is the temperature of the phase transition from the tetragonal D0₂₂ structure to the hexagonal D0₁₉ structure. Despite its low magnetization, the large coercive field in Mn₃Ge represents an opportunity to study exchange-spring magnets consisting of soft and hard magnetic phases.