Permanent magnetic properties of Nd-Fe-B melt-spun ribbons with Y substitution

Phase constituents, microstructures and magnetic properties of melt-spun Nd12-xYxFe81B6Nb ribbons were investigated systematically. The influence of Y substitution for Nd on the phase stability, grain size and magnetic exchange coupling was analyzed. It is found that all the ribbons crystallize in the tetragonal 2:14:1 structure, i.e., with single hard magnetic phase at the roll speed of 25 m center dot s(-1). With the increase in Y doping, Curie temperature (T-C) increases, while the coercivity decreases monoclinically. However, remanence magnetization (B-r) and maximum energy product ((BH)(max)) fluctuate and the maximum value is obtained at certain amount of Y. The optimum magnetic properties of intrinsic coercivity of intrinsic coercivity (H-cj) = 908.2 kA center dot m(-1) and (BH)(max) = 118.52 kJ center dot m(-3) are achieved when x = 1.0. It can be attributed to the strengthened exchange coupling between the neighboring nanograins in Nd-Y-Fe-B melt-spun powder based on the Henkel curves. Furthermore, Y substitution also significantly improves the temperature stability of magnetic performance. The coercivity temperature coefficient of beta = - 0.157%center dot degrees C-1 and remanence temperature coefficient of alpha = - 0.32%center dot degrees C-1 are gained, which are greatly reduced compared with those of the undoped Nd-Fe-B compounds.