NdFeB magnets with higher Curie temperature

Substitution of cobalt for iron increases the Curie temperature (T
c
) of NdFeB alloy but the anisotropy field (H
A
) and the intrinsic coercivity force (H
ci
) was found to decrease rapidly [1]. Aluminum was found to be effective in increasing H
ci
of NdFeCoB alloys. However, aluminum decreases the saturation magnetization (M
s
) and T
c
of these alloys. A systematic study of the effect of aluminum substitution on the magnetic properties of NdFeCoB system has been completed. Higher boron level is found necessary to stabilize the magnetic phases in NdFeCoAlB alloys. A NdFeCoAlB magnet with a T
c
of 430°C, B
r
of 9,300 Gauss, H
c
of 9,100 Oe, H
ci
of 18,000 Oe and
BH_{\max}
of 21.6 MGOe was obtained. Nickel addition to the NdFeCoB system increases both M
s
and T
c
. Primary magnetic properties of NdFeCoMB, where M = Al or Ni, are also presented.