Influence of Co substitution in exchange coupled NdFeB nanocrystalline permanent magnets

Nanocrystalline exchange coupled Nd-2(Fe1 - xCox)(14)B single phase, Nd-2(Fe1 - xCox)(14)B + (Fe1 - xCox) composite magnets and exchange decoupled Nd-2(Fe1 - xCox)(14)B magnets with overstoichiometric Nd (all with x = 0.12 and 0.24) have been produced using the melt-spinning procedure. Both, single phase and composite magnets show a significant remanence enhancement (J(R) greater than or equal to J(S)/2) and high maximum energy products of up to 175.8 kJ/m(3), compared to 93.3 kJ/m(3) for the exchange decoupled magnet (both at 300 K). By substituting Co for Fe in the Nd2Fe14B the Curie temperature raises to 780 K for the 20 at% Co-substituted material and maximum energy products of almost 120 kJ/m(3) are achieved at 435 K. (C) 1999 Elsevier Science B.V. All rights reserved.