We have investigated the normal-state resistance and the excess low-frequency (1/f) noise in 45° tilt [001] grain-boundary junctions in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ thin films. A characteristic temperature dependence of the resistance fluctuations and a linear temperature dependence of the grain-boundary resistance (with a negative temperature coefficient) emerge as common features. These observations are quantitatively compared with a model of many, parallel conduction paths across the boundary, taking into account both temperature-independent and thermally activated transport processes.

• Received 11 August 1994

DOI:https://doi.org/10.1103/PhysRevB.51.16164