Universal conductance fluctuations and low-temperature $1/f$ noise in mesoscopic AuFe spin glasses

We report on intrinsic time-dependent conductance fluctuations observed in mesoscopic AuFe spin-glass wires. These dynamical fluctuations have a $1/f$-like spectrum and appear below the measured spin-glass freezing temperature of our samples. The dependence of the fluctuation amplitude on temperature, magnetic field, voltage, and Fe concentration allows a consistent interpretation in terms of quantum interference effects, that are sensitive to the slowly fluctuating spin configuration.