Nanocomposite Nd2(Fe,Co,Cr)14B/α-Fe materials

We report on magnetic properties of high-energy ball-milled and annealed Nd12.6Fe69.8-xCo11.6CrxB6/alpha-Fe (0 less than or equal to x less than or equal to 6), powders with excess alpha-Fe. Increasing chromium content leads initially to an increase in intrinsic coercivity, giving a maximum at x = 2, while remanent magnetic polarization decreases considerably. The principal advantage of the Co addition is increase in the Curie temperature and intrinsic coercivity, H-J(c), of the hard phase and an increase in the saturation polarization arising from the higher saturation of (Fe,Co) compared to that of pure alpha-Fe. For Nd12.6Fe67.8Co11.6Cr2B6/alpha-Fe with a 37.5% volume fraction of alpha-Fe, a remanent magnetic polarization of 1.1 T and an intrinsic coercivity of 760 kA m(-1) wen achieved. The powders are of potential use in the manufacture of polymer-bonded magnets. (C) 1998 Elsevier Science B.V. All rights reserved.