Suppression of Magnetic Flux Noise in YBa2Cu3O7−x Flux Transformers
We have constructed hybrid magnetometers by coupling a flux transformer of YBa2Cu3O7−x to a Nb-Pbln SQUID. The low frequency (1/f) noise is dominated by fluctuations in the supercurrent circulating in the transformer, driven by vortex motion. The application of a small static magnetic field induces a supercurrent that reversibly suppresses the noise, in quantitative agreement with a model of thermally activated vortex hopping between symmetrical pairs of pinning sites. A persistent current can be used to reduce the low frequency noise power of high-Tc flux transformers by at least one order of magnitude.
KeywordsNoise Power Vortex Motion YBCO Film Persistent Current Field Sensitivity
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