Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 19: Mikro- und nanostrukturierte magn. Materialien I
MA 19.5: Vortrag
Montag, 7. März 2005, 11:30–11:45, TU EMH225
Structure and Magnetic Properties of Nanocrystalline Fe100−xPtx Powders — •Julia Lyubina, Oliver Gutfleisch, Karl-Hartmut Müller, and Ludwig Schultz — IFW Dresden, Institute for Metallic Materials, P.O. Box 270016, D-01171 Dresden, Germany
The ordered tetragonal L10 FePt phase has excellent intrinsic magnetic properties (K1 = 6.6 MJm−3, Js = 1.43 T, Tc = 750 K), good mechanical properties and corrosion resistance. The combination of these unique properties makes it interesting both from the scientific and application points of view. Here we report on the preparation of nanocrystalline hard magnetic Fe100−xPtx (x = 39.5; 45; 50; 55; 60) powders by mechanical ball milling at 77 K followed by annealing (450 0C). According to Rietveld refinement of x-ray data, annealed powders contain a mixture of the highly ordered L10 FePt and disordered cubic A1 FePt, as well as Fe3Pt and FePt3. The amount of the A1 FePt phase remains almost unchanged (6-10 vol. %), whereas the fraction of the L10 FePt, Fe3Pt and FePt3 phases varies with Pt concentration x. Coercivity µ0Hc was found to increase with Pt concentration from 0.33 T (x = 39.5) to 0.95 T (x = 60), whereas remanence Jr reduce: from 0.8 T (x = 39.5) to 0.4 T (x = 60). In Fe-rich powders exchange-spring behaviour was observed. The evolution of magnetic properties is discussed in terms of phase composition, distribution of the phases and degree of chemical order.