REENTRANT SPIN-GLASS ORDERING IN FCC CU0.74FE0.26 ALLOYS

The temperature dependence of the low-field magnetization and of Mossbauer spectra has been observed for a high-Fe-concentrated fcc Cu0.74Fe0.26 alloy. At low temperatures, the zero-field-cooled and field-cooled magnetization show different thermomagnetic behavior. The average hyperfine field was found to increase with decreasing temperature below the Curie-temperature T(c) of about 240 K. An additional increase is observed below the freezing ("spin-canting") temperature T(f) of about 40 K. In Mossbauer spectra measured in longitudinal external magnetic fields, the second and fifth lines of the sextet (i.e. the DELTA-m = O-nuclear transitions) appear below T(f), while they disappear above T(f). These results indicate that the present alloy is a reentrant spin-glass system, characterized by freezing of transverse spin components below T(f).