Mechanical Relaxations, Spin Glasses and 1/F Resistance Noise

Two experiments related to 1/f resistance noise will be described in this thesis. The first is measurements of the anelastic piezoresistance in thin films of bismuth, niobium and iron to demonstrate a connection between mechanical anelastic relaxations and electrical 1/f noise from the motion of defects. We have found that the connection between 1/f noise and mechanical relaxation is more complex than was originally believed and depends critically on the relevant electronic and mechanical coupling factors. The broad nature of 1/f noise is due not to a fundamental source but the generally poor quality of thin films. The second experiment examines resistance changes in mesoscopic samples of the spin glass CuMn. A large sensitivity of the resistance to the relative configuration of spins in the sample was found with a magnitude and temperature dependence in accordance with predictions of universal conductance fluctuations. Predictions of the droplet theory of spin glasses were tested and no evidence was found for chaotic behavior with temperature changes. These results, and others, are more consistent with hierarchical models for the spin glass phase space.