High coercivity Dy substituted Nd-Fe-Co-B magnetic nanoparticles produced by mechanochemical processing

摘要

(Nd1-xDyx)(2)(Fe,Co)(14)B magnetic nanoparticles, in a range of Dy content from 0 to 0.6, were synthesized by a mechanochemical process. The influence of Dy substitution on the crystal structure and magnetic properties were studied. With increasing Dy content, the coercivity of (Nd1-xDyx)(2)(Fe,Co)(14)B particles first doubled from 8.8 kOe (x = 0) to a high value of 17.8 kOe (x = 0.5), further increase of Dy content led to a slightly lower coercivity of 17.5 kOe (x = 0.6). (Nd0.8Dy0.2)(2)(Fe,Co)(14)B particles exhibited good thermal stability, with a thermal coefficient of remanence (alpha) of -0.053% and thermal coefficient of coercivity (beta) of -0.348%. Reduced spin-reorientation temperatures (T-SR) of 105 K - 115 K were observed for (Nd1-xDyx)(2)(Fe,Co)(14)B, for x in the range of 0 to 0.2, making these compositions more attractive for cryogenic applications. Detailed analysis of the temperature dependent magnetic properties revealed that coercivity was controlled by nucleation of reversed magnetic domains.