Abstract
ac magnetoresistance measurements of low-strain epitaxial films of on substrate show an out-of-phase response which switches sign near the metal-insulator transition, indicating at least two types of slow contributors to the magnetoresistance and suggesting the role of a third phase. These films show noise properties very distinct from films under tensile strain. A narrow peak in the noise found at the transition is non-Gaussian but lacks distinct persistent few-state fluctuators. Such fluctuators only appear some below the transition, indicating that conduction in the nominally metallic phase remains highly inhomogeneous. Comparison of discrete fluctuator sizes in a range of materials indicates that strain constraints limit the sizes in films.
3 More- Received 3 June 2004
DOI:https://doi.org/10.1103/PhysRevB.71.014423
©2005 American Physical Society