Microstructural changes during the slow-cooling annealing of nanocrystalline SmCo 2:17 type magnets

作者：Romero S A; de Campos M F^*; de Castro J A; Moreira A J; Landgraf F J G

来源：Journal of Alloys and Compounds, 2013, 551: 312-317.

DOI：10.1016/j.jallcom.2012.08.131

• SmCo magnets
• Anisotropy field
• Stoner-Wohlfarth model
• Heat treatment

The microstructure and magnetic properties of 2:17 type isotropic magnets were investigated. The slow cooling heat treatment (cooling at 1 degrees C/min from 820 to 400 degrees C, and isothermal treatment during 24 h) was interrupted after the temperatures of 820, 700, 600 and 500 degrees C and their hysteresis were measured with fields up to 9 T. The fully heat treated sample presented coercivity (mu H-0) of 3.32 T, after 24 h at 400 degrees C. The microstructure was investigated with SEM-FEG (Scanning Electron Microscope with Field Emission Gun) and X-ray Diffraction Rietveld analysis. The application of the Stoner-Wohlfarth-Callen-Liu-Cullen (SW-CLC) model points out exchange coupling between ferromagnetic Sm-2(CoFe)(17) nanocells and ferromagnetic Sm(CoCu)(5) present at the cell boundary phase. The results are interpreted with the double shell model: first-a cobalt-rich ferromagnetic Sm(CoCu)(5) shell originates exchange coupling and second-a copper-rich paramagnetic Sm(CuCo)(5) shell produces magnetic decoupling. This double shell helps to maximize coercivity and remanence. The anisotropy field of the Sm-2(CoFe)(17) cell phase was estimated in 7 T with the SW-CLC model.

• 出版日期2013-2-25