Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 24: Magnetic Materials I
MA 24.9: Vortrag
Mittwoch, 18. März 2015, 11:45–12:00, H 0112
Phase Formation and Hot Compaction of Mn-Ga L10 Hard Magnets — •Torsten Mix1,2, Ludwig Schultz1,2, and Thomas George Woodcock2 — 1IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden, Germany — 2Department of Physics, TU Dresden, Dresden, Germany
The Mn-Ga binary system contains phases with high magnetocrystalline anisotropy, which may be suitable candidates for rare earth free permanent magnets. Depending on the composition, L10 (cP4; P4/mmm) or D022 (tI8; I4/mmm) structured phases can be produced. The aim of this work is to understand the formation and stability of the L10 phase and to optimise both the intrinsic and extrinsic magnetic properties of the alloys. Mn-Ga binary alloys with compositions in the range 55-65 at.% Mn were produced by arc melting and annealing. Phase formation was studied using thermal analysis, x-ray diffraction and magnetometry. Measurements of the magnetocrystalline anisotropy constant and anisotropy field were performed in applied magnetic fields of 14 T. An improvement in the Hc of the Mn-Ga alloys was obtained by producing powder from bulk L10 materials by mechanical milling. The L10 powder had a similar magnetisation but a fivefold higher Hc compared to the bulk sample (cf. Mn60Ga40: powder: Hc = 0.376 T, bulk: Hc = 0.073 T). Partial alignment of the L10 powder in a magnetic field was possible, giving a possible route to the production of anisotropic magnets. Furthermore, fully dense, isotropic, hot compacts were produced in which the improved magnetic properties of the powders were retained.