Enhancement of magnetic properties of nanocomposite Pr2Fe14B/alpha-Fe magnets by small substitution of Dy for Pr

Nanocomposite (Pr,Dy)(2)Fe14B/alpha -Fe magnets with compositions Pr8-xDyxF e86B6 (x = 0, 0.5, 1, 1.5, and 2) have been synthesized by melt spinning us ing low wheel speeds in the range from 18 to 21.7 m/s. It has been found th at the coercivity is significantly increased by Dy substitution. An optimum coercivity of 6.6 kOe is obtained in the Pr7Dy1Fe86B6 magnet as compared t o 4.3 kOe in the Pr8Fe86B6 magnet. As a result, the energy product is incre ased from 9.1 MGOe in the Pr8Fe86B6 magnet to 16.9 MGOe in the Pr7Dy1Fe86B6 magnet. The reason for this is the finer and more uniform 2:14:1/alpha -Fe nanoscale microstructure developed in the magnets with Dy substitution. Be cause of the low wheel speed spinning, the majority of the nanoscale micros tructure is crystallized directly out of the melt. The enhancement of magne tic properties by Dy substitution is mainly due to the microstructure refin ement which leads to an enhanced exchange coupling between the Pr2Fe14B and alpha -Fe, whereas the anisotropy increase by the Dy substitution provides only a minor contribution to the enhanced coercivity. (C) 2001 American In stitute of Physics.