Microstructure and exchange coupling in nanocrystalline Nd_2(FeCo)_(14)B/α-FeCo particles produced by spark erosion

摘要

Exchange spring magnet particles of Nd_2(FeCo)_(14)B/α-FeCo were prepared by spark erosion. X-ray diffraction and Moessbauer studies showed that the particles are composed of about ～85 vol % of Nd_2(FeCo)_(14)B and ～13 vol % of α-FeCo with negligible other phases. No oxide was found in these particles. Transmission electron micrographs indicated that the grain sizes of the Nd_2(FeCo)_(14)B and α-FeCo phases are ～10-50 nm, and are compatible with effective exchange coupling between the hard and soft phases. The intergrain exchange coupling was also observed in ΔM measurements.