Magnetic properties of mechanically alloyed FeCu

The temperature dependence of saturation magnetization has been observed for an unstable FCC Fe 50 Cu 50 solid-solution sample prepared by mechanical alloying. The unstable Fee Fe 50 Cu 50 solid solution has a Curie temperature of 505+or-5 K. At low temperatures the saturation magnetization is well approximated by the relationship M(T)=M(0)(1-BT 3 2/), where M(0)=108.7 emu g -1 and B=4.21*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 Fe 50 Cu 50 solid solution was observed. The magnetic moment of Fe atoms in the FCC Fe 100-x Cu x Phases remains at about 2.35 mu B for 50<x<61, and drops rapidly to 0.544 mu 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 Fe 29.3 Cu 70.7 solid solution falls to about 200 K.