Electrical noise in the spin-glass AuFe

Measurements of electrical resistance fluctuations have been performed on the spin-glass AuFe in order to compare with prior results in CuMn. Macroscopic AuFe samples showed a sharp increase in the noise with the onset of the noise at a temperature corresponding to the peak in the magnetic susceptibility as a function of temperature. This temperature is identified as the transition into the spin-glass phase. Measurements on mesoscopic AuFe samples showed significantly different behavior than mesoscopic CuMn samples, due to the large anisotropy introduced by the gold. AuFe samples showed persistent two-state behavior which indicates a smaller number of states being available to the system than in CuMn which never had stable first spectra. Some of these stable spectral features could be tracked through a temperature range of several degrees enabling the calculation of activation energies and attempt rates. Thermal cycles above the spin-glass temperature caused much less variability in the resistance fluctuation spectrum and the resistance than in CuMn. Second spectrum measurements failed to fit AuFe clearly into either a hierarchical or interacting droplet picture, although this part of the data was more closely identifiable with the hierarchical predictions.U of I OnlyETDs are only available to UIUC Users without author permissio