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

The magnetic properties and microstructural evolution of (Nd1-xLax)(9.5)Fe85.5B5 (x = 0, 0.05, 0.10 and 0.15) 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 Nd2Fe14B and alpha-Fe phases of fine grains. B-r of 9.9 kG, H-i(c) of 6.2 kOe and (BH)(max) = 15.5 MGOe have been obtained in the alloy ribbons with x = 0.10 when directly quenched at a wheel speed of 18 m/s.