MAGNETIC-PROPERTIES OF MECHANICALLY ALLOYED FECU

The temperature dependence of saturation magnetization has been observed for an unstable FCC Fe50Cu50 solid-solution sample prepared by mechanical alloying. The unstable FCC Fe50Cu50 solid solution has a Curie temperature of 505 +/- 5 K. At low temperatures the saturation magnetization is well approximated by the relationship M(T) = M(0)(1 - BT3/2), where M(0) = 108.7 emu g-1 and B = 4.21 x 10(-5) K-3/2. This holds over a large temperature range (T/T(C) < 0.4) indicating the presence of long-wavelength spin-wave excitations and disordered atomic structure. On annealing the as-milled sample at annealing temperatures above about 500 K, decomposition of the metastable FCC Fe50Cu50 solid solution was observed. The magnetic moment of Fe atoms in the FCC Fe100-xCux phases remains at about 2.35mu(B) for 50 < x < 61, and drops rapidly to 0.544mu(B) for x = 70.7. This results in the 40% reduction of the saturation magnetization at zero temperature for the sample annealed at 673 K for 1 h when compared to that for the as-milled sample. The Curie temperature of the FCC Fe29.3Cu70.7 solid solution falls to about 200 K.