Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 3: Magnetische Materialien

MA 3.8: Vortrag

Montag, 24. März 2003, 12:00–12:15, HSZ/401

Influence of Low Temperature Magnetic Phase Transitions on the Properties of (Nd,Pr,Dy)-(Fe,Co)-B Magnets — •Julia Lyubina, Axel Handstein, Oliver Gutfleisch, Dietrich Hinz, Manfred Wolf, Konstantin Nenkov, Dieter Eckert, Karl-Hartmut Müller, and Ludwig Schultz — Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, PO Box 270116, D-01171 Dresden, Germany

Low-temperature magnetic phase transitions need to be considered when developing high performance permanent magnets for superconducting bearings or motors. Magnetic transitions such as spin reorientation transition (SR) and an onset of first order magnetization process (FOMP) in different kinds of samples (as-cast alloys, epoxy bonded aligned powders, die-upset magnets) made from Nd_xPr_14.7−xFe_77.3B₈ and Pr_14.7(Fe_1−xCo_x)_77.3B₈ alloys (x = 0; 0.25; 0.5; 0.75; 1) were investigated at low temperatures. In Nd_xPr_14.7−xFe_77.3B₈ the linear decrease of the SR temperature with increasing Pr content was observed. The onset of the SR observed in the second quadrant demagnetisation curves of die-upset Nd containing magnets starts at higher temperatures compared to ac susceptibility (χ_ac) measurement results. No influence of FOMPs on permanent-magnet properties of (Nd,Pr,Dy)-(Fe,Co)-B magnets was observed. For Pr_14.7(Fe_1−xCo_x)_77.3B₈ (x = 0.25; 0.5) an anomaly in the ac susceptibility was found at 14 K. This low temperature peak was also found in Dy containing Pr-(Fe,Co)-B magnets. The anomaly is attributed to the addition of Co and is not of SR origin.