A systematic study of die-cast REFeAl (RE=Nd+Pr) bulk amorphous alloys with small B, Cu, and Dy additions is presented. Differential scanning calorimetry and x-ray diffraction data are consistent with an amorphous microstructure and a small amount of hcp Nd-type crystallites embedded in the amorphous matrix for B, Cu+B-, and Dy-containing alloys. Coercivity, Hc, exhibits a progressive enhancement upon B, B+Cu, and Dy addition (from 284 kA/m for Nd30Fe60Al10 up to 388 kA/m for Dy substituted alloy). This Hc improvement is associated not only with domain wall pinning on the crystallites, but also with the increase of nucleation sites and thus, with the number of RE and RE–Fe–Al clusters. In agreement with the latter, a superparamagnetic behavior, which is characteristic of a clustered structure, was observed above 451 K for all the alloy compositions.
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