Relaxation of Microwave Nonlinearity in a Cuprate Superconducting Resonator

The second- and third-order nonlinear microwave response of a superconducting YBa₂Cu₃O₇ thin-film resonator was synchronously measured using three input tones. This technique permits the local measurement, and hence mapping, of intermodulation distortion inside the resonator. Second- and third-order IMD measured with a fixed probe relaxed in remarkably different ways after the removal of a static magnetic field. The second-order IMD relaxed by two different magnetic processes, a fast process that appears related to bulk remanent magnetization and a slow process that fits the description of Bean and Livingston. The third-order IMD relaxes by only one process that is distinct from the two processes controlling second order relaxation.