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https://hdl.handle.net/2142/21867
Description
Title
Electrical noise in the spin-glass gold-iron
Author(s)
Meyer, Karl Alan
Issue Date
1994
Doctoral Committee Chair(s)
Weissman, Michael B.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Condensed Matter
Language
eng
Abstract
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.
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