The structure and magnetostriction of (Tb1-xNdx)(Fe0.4Co0.6)(1.9) (0 < x <
1) alloys have been investigated at room temperature and the magnetic prope
rties determined over the temperature range 1.5-300 K. It was found that th
e matrix of (Tb1-xNdx)(Fe0.4Co0.6)(1.9) is essentially that of a (Tb,Nd) (F
e,Co)(2) phase with a MgCu2-type cubic Laves structure for all values of x.
The lattice parameter of the Laves phase increases from 0.7297 to 0.7363 n
m as x increases from 0 to 1 and obeys Vegard's law. We have measured the C
urie temperature to decrease with increasing x from 667 K for Tb(Fe0.4Co0.6
)Fe-1.9 to 454 K for Nd(Fe0.4Co0.6)Fe-1.9. The resultant macroscopic magnet
ization becomes zero when x = 0.45 at a temperature of 1.5 K. At 300 K, a s
lightly smaller value of x is found to produce no resultant magnetization,
and the spontaneous magnetostriction constant lambda(111) decreases slowly
with increasing Nd content and vanishes abruptly from a value of 1630 x 10(
-6) when x > 0.65. The polycrystalline isofield magnetostriction curves exh
ibit a minimum at x = 0.45 and a peak at x = 0.65. The observed behavior ca
n be explained on the basis of opposing rare-earth Tb and Nd moments and an
anisotropy minimum close to x = 0.65. As the temperature is reduced below
300 K, the spin reorientation occurs at greater Nd concentrations. (C) 1999
American Institute of Physics. [S0021-8979(99)05423-7].