The effects of La-substitution on the microstructure and magnetic properties of nanocomposite NdFeB melt spun ribbons

Abstract The magnetic properties and microstructural evolution of (Nd 1− x La x ) 9.5 Fe 85.5 B 5 (x = 0, 0.05, 0.10and0.15) melt spun ribbons have been investigated. It was found that La is effective in refining the grain size of these ribbons. La-substitution is also effective in yielding excellent magnetic properties even when the alloy is melt spun at a lower wheel speed. The magnetic properties of the ribbons are determined by two major factors: (1) the magnetic dilution and (2) the enhancement of exchange coupling between Nd 2 Fe 14 B and α-Fe phases of fine grains. B r of 9.9 kG, i H c of 6.2 kOe and (BH) max = 15.5MGOe have been obtained in the alloy ribbons with x = 0.10 when directly quenched at a wheel speed of 18 m/s.