Preparation of the exchange-spring permanent magnet composite ultrastrong permanent magnet with ultrastrong energy products

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Preparation of nanocomposite magnets composed of SmCo_5 as a hard magnetic phase andα-Fe powders and subsequent heat treatment for crystallization. The amount of the soft α-Fe phase was varied, and the effects of Fe content on the magnetic properties have been investigated. The mechanically alloyed (SmCo_5)_<1-x>Fe_x powders were found to be composed of the Sm-Co amorphous phase and α-Fe phase. The composite of a SmCo_5 phase (1-5 phase) andα-Fe phase obtained by heat treatment at 823 or 873K. On the other hand, after crystallization at 923 or 1073K, the 2-17 phase was formed instead of the 1-5 phase. The (SmCo_5)_<1-x>Fe_x powders crystallized at 873K showed fine microstructures composed of grains 10-20 nm in size. The values of remanence Mr of (SmCo_5)_<1-x>Fe_x powders significantly increased with increasing Fe content, on the other hand, the values of coercivity linearly decreased. The maximum value of maximum energy product, 105.8 kJ/m3, was obtained for the (SmCo_5)_<75>Fe_<25> powder. In the demagnetization curves of the (SmCo_5)_<1-x>Fe_x powders in the second quadrant, any step due to the presence of soft phase was not detected and the recoil loops showed a large reversible magnetization reaching about 60 %. From these results, it is evident that exchange coupling between the soft and hard phase was obtained in this study.