Electrical noise from spin fluctuations in CuMn

Low-frequency resistance fluctuations in thin films of ${\mathrm{Cu}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$ (0.045≤x≤0.195) were found to grow dramatically as the films were cooled through the magnetic freezing temperature. The temperature dependence, magnetic field dependence, x dependence, and magnitude of the noise indicated it came from spin fluctuations, probably coupled to resistivity mainly via universal conductance fluctuations. Theoretical problems are discussed, as are future experiments on fundamental properties of spin glasses.