Giant magnetoresistance in the disordered magnetic alloy (FeNi)25Au75

We present the results of detailed measurements of the field and temperature dependence of the magnetization and the resistivity of the (FeNi)${}_{25}$Au${}_{75}$ alloy, belonging to the fcc (FeNi)${}_{100-x}$Au${}_x$ $(x=25\mathrm{}$, 45, 60, 75) system. Giant magnetoresistance (GMR) has been observed only in the $x=75\mathrm{}$ alloy, where the magnetic relaxation, thermoremanent magnetization, and hysteresis data suggest reentrant spin-glass-like behavior at low temperatures. The origin of GMR in (FeNi)${}_{25}$Au${}_{75}$ is attributed to the field-induced alignment of Fe moments. The data suggest a subtle link between frustration and GMR in disordered magnetic materials.