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

Abstract

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.