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 of25 m s-1.With the increase in Y doping,Curie temperature(Tc) increases,while the coercivity decreases monoclinic ally.However,remanence magnetization(Br) 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(Hcj)=908.2 kA·m-1and(BH)max=118.52 kJ·m-3are achieved when x=1.0.It can be attributed to the strengthened exchange coupling between the neighboring nanograins in Nd-Y-Fe-B meltspun powder based on the Henkel curves.Furthermore,Y substitution also significantly improves the temperature stability of magnetic performance.The coercivity temperature coefficient of β=-0.157%·℃-1and remanence temperature coefficient of α=-0.32%·℃-1are gained,which are greatly reduced compared with those of the undoped Nd-Fe-B compounds.