Microwave absorption and intermittency in textured Y 1Ba 2Cu 3O 7−x thin films

Abstract

We report simultaneous measurements of direct and field-modulated microwave absorption in textured Y 1Ba 2Cu 3O 7−x thin film and ceramic samples. The two techniques are shown to monitor two different characteristic onset temperatures in the superconducting system. Below the critical transition temperature T c, the modulated signal shows noise-like fluctuations whose onset temperature T ∗ decreases logarithmically with the amplitude of the modulation field. These results are ascribed to a distribution of weak Josephson links. Intermittent very low frequency microwave absorption jumps of constant amplitude are observed at fixed temperatures, and are similar to the predicted behaviour of an ideal Josephson junction shunted with a capacitor and a resistor.