Effects of additional elements on the structure and magnetic properties of Nd2Fe14B/α-Fe-type nanocomposite magnets

The effects of a partial substitution of Mo, Ga, Si or Al, respectively, for Fe on the structure and magnetic properties of Nd-8.4 Fe-87.1 BJ(4.5) alloy prepared by mechanical alloying have been studied in detail. The addition of 1.1 at% Mo, Si or Ga results in the improvement of the intrinsic coercivity of the nanocomposite magnets. In contrast, the substitution of 1.1 at% Al is unfavourable for improving the magnetic properties. The optimum average grain size d(op) of the alpha-Fe is different for various element substitutions. It is found that in addition to the grain size of alpha-Fe. the grain size of Nd2Fe14B is another important factor in determining the magnetic properties of nanocomposite magnets. The main effects of these substitutions on the magnetic properties of the nanocomposite magnets originate Rom modifications of the grain sizes of the soft magnetic phase and the hard magnetic phase. The best magnetic properties: mu(0)H(c) = 0.4 T (4 kOe), J(r) = 1.07 T (10.7 kGs), (BH)(max) = 93.2 kJ m(-3) (11.7 MGOe), J(r)/J(s) = 0.68, are achieved for the Nd8.4Fe86Ga1.1B4.5 alloy.