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MA: Fachverband Magnetismus

MA 2: Magnetic Materials I

MA 2.1: Vortrag

Montag, 7. März 2016, 09:30–09:45, H31

Analysis of Local Magnetisation, Composition, and in Situ Magnetization Reversal in (Dy,Nd)-Fe-B Core-Shell Sintered Magnets — •Tim Helbig¹, Konrad Löwe¹, and Oliver Gutfleisch^1,2 — ¹TU Darmstadt, Functional Materials — ²Fraunhofer IWKS Hanau, Germany

One approach to reduce the amount of expensive heavy rare earth elements (RE), such as Dy or Tb, in permanent magnets is to design the grain boundaries of modern high performance NdFeB-type magnets. Their grains consist of a heavy RE rich shell and a Nd₂Fe₁₄B core. Heavy REs are needed to provide high coercivity especially at elevated temperatures, they reduce however the total magnetic moment at the same time. The idea of the shell structures is to use as little Dy as necessary to improve the coercivity of the entire magnet by only concentrating Dy at the "weak point" i.e. the grain boundary. In this work, a core-shell structured (Dy,Nd)-Fe-B sintered magnet was produced through a novel experimental technique involving blending of powders with different compositions and grain sizes and analysed by Scanning Electron Microscope (SEM), Magnetic Force Microscopy (MFM) and Kerr microscopy. It was possible to correlate all used characterisation methods on the same specific area and match chemical composition with local magnetisation. Further, in situ magnetization reversal using MFM and Kerr with externally applied magnetic fields were employed.