Interaction Effects on the Appearance of a Magnetic Moment on Co, Through Nuclear Specific-Heat Measurements on Au:Co Alloys

The specific heat of Au:Co alloys down to 0.02 K is reported. The nuclear term ($A{T}^{-2\mathrm{}}$) is due to the magnetic Co atoms which are found to be those included in groups of three and more neighbors. The low-temperature linear term ($\gamma T$) is the sum of the contributions of the magnetic Co groups, nonmagnetic pairs, and isolated atoms. We estimate fluctuation temperatures of 50 K for the pairs and 700 K for the isolated atoms.