Enhanced formation of 2:14:1 phase in La-based rare earth-iron-boron permanent magnetic alloys by Nd substitution

Aiming at promoting the formation of hard magnetic 2:14:1 phase in La-Fe-B alloys, the effects of Nd substitution on the melt-spun nanocrystalline (La1-xNdx)yFe94-yB6 alloys (x = 0-0.5; y = 12-16) have been investigated. No hard magnetic phase was formed in the (La1-xNdx)16Fe78B6 alloys with x < 0.2. A soft magnetic phase (La,Nd)2Fe23B3 with Curie temperature of 649 K was observed in the x = 0.2 alloy and it disappeared as x increased to 0.3. 30% and above Nd substitution can dramatically enhance the formation of 2:14:1 phase and the magnetic properties of La-based permanent magnets. Three different alloy systems (y = 16, 14 and 12) show similar behavior of magnetic properties dependences on Nd substitution. (La0.7Nd0.3)16Fe78B6 alloy with mean grain size 10-20 nm exhibits high remanent magnetization, maximum energy product and intrinsic coercivity up to 0.71 T, 10.0 MGOe and 562 kA/m, respectively, indicating it is possible to achieve excellent magnetic properties in La-based rare earth permanent magnets. The present work provides a good understanding on the fundamental magnetism of La-based magnets and the potential to develop low cost rare earth permanent magnets.