Regensburg 2002 – wissenschaftliches Programm
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MA: Magnetismus
MA 8: Hart- und Weichmagn. Materialien / Legierungen
MA 8.2: Vortrag
Dienstag, 12. März 2002, 14:00–14:15, H10
High performance nanocrystalline (Pr,Nd)FeB-based magnets produced by intensive milling — •A. Bollero1, O. Gutfleisch1, K.-H. Müller1, L. Schultz1, G. Drazic2, and S. Kobe2 — 1IFW Dresden, Institut für Metallische Werkstoffe, Postfach 270116, D-01171 Dresden, Germany — 2Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia
Intensive milling has been used to produce nanocrystalline isotropic (Pr,Nd)FeB-based powders. The influence of Dy and Zr, and the substitution of Pr by Nd, on the structural and magnetic properties have been studied. Reduction of R-content, increase of T-content and presence of Co in the starting composition led to an improved performance: Jr = 0.92 T, µ0Hc = 1.25 T and (BH)max = 140 kJ/m3 for Pr9Nd3Dy1Fe72Co8B6.9Zr0.1 due to a fine microstructure with a mean grain size of 20 nm. Intensive milling has shown to be a versatile technique to produce high performance nanocomposite magnets by blending this alloy with different fractions of α-Fe. 25wt.%Fe addition resulted in an optimum combination of magnetic properties with (BH)max = 178 kJ/m3 due to an effective exchange coupling between the hard and soft magnetic phases. A TC of about 365∘C was found. Demagnetization recoil loops of both, single-phase and nanocomposite magnets, showed clear differences due to the exchange-spring mechanism present in the latter. δJ plots for the nanocomposite magnets showed a negative deviation of the demagnetizing remanence from the Wohlfarth model indicative of exchange coupling interactions being dominant.