GIANT MAGNETORESISTANCE IN THE DISORDERED MAGNETIC ALLOY (FENI)(25)AU-75

We present the results of detailed measurements of the field and tempe rature dependence of the magnetization and the resistivity of the (FeN i)(25)Au-75 alloy, belonging to the fcc (FeNi)(100-x)Au-x (x=25, 45, 6 0, 75) system. Giant magnetoresistance (GMR) has been observed only in the x=75 alloy, where the magnetic relaxation, thermoremanent magneti zation, and hysteresis data suggest reentrant spin-glass-like behavior at low temperatures. The origin of GMR in (FeNi)(25)Au-75 is attribut ed to the field-induced alignment of Fe moments. The data suggest a su btle link between frustration and GMR in disordered magnetic materials .