Temperature dependence of magnetic properties for nanocomposite Nd-2(Fe,Co,M)(14)B/alpha-Fe magnets

High-energy ball-milled and heat-treated Nd12.6Fe69.8-xCo11.6MxB6/alpha-Fe and Nd16Fe66.4-xCo11.6MxB6/alpha-Fe (M = Zr with x = 0.5 and Al-1 Cr-2) pow ders, with an excess of alpha-Fe (10 and 37.5 vol%), have been compacted by hot pressing to forts magnets. Hot pressing at 1070K of Nd12.6Fe69.3Co11.6 Zr0.5B6/alpha-Fe and Nd16Fe65.9Co11.6Zr0.5B6/alpha-Fe powders, containing 3 7.5 vol% alpha-Fe, resulted in isotropic magnets with J(r) = 0.99 T, H-J(c) = 430 kA m(-1), rho similar to 7.59 g cm(-3) and J(r) = 0.95 T, H-J(c) = 5 10 kA m(-1), rho similar to 7.61 g cm(-3), respectively. Temperature coeffi cients (from 293 to 413 K) of remanence alpha(J(r)) and coercivity beta(H-J (c)) of these magnets are: -0.07% K-1, -0.35% K-1 and -0.07% K-1, -0.37% K- 1, respectively. The values of alpha and beta are smaller than those of sin tered Nd-Fe-B magnets. (C) 2000 Elsevier Science B.V. All rights reserved.