Magnetic Flux Noise of the Vortex Lattice Melting Transition in Bi_2Ba_2CaCu_2O_8+δ
Abstract
We have measured the spectral density of magnetic flux noise, S_Φ(f), associated with the vortex lattice melting transition in a single crystal of Bi_2Ba_2CaCu_2O_8+δ. The noise was measured by a niobium Superconducting QUantum Interference Device (SQUID) inside a vacuum can and thermally anchored to a liquid helium bath, but thermally isolated from the sample. The sample, of dimensions 1.3 mm × 1.3 mm × 30 μm, was mounted on a variable temperature stage and placed less than 100 μm away from the SQUID. The sample was cooled in magnetic fields up to 5 mT, and S_Φ(f) was measured as a function of field and temperature. In the larger fields, S_Φ(f) showed a peak at a temperature well below Tc and exhibited qualitatively different spectra above and below the peak. The temperature at which the noise peak occurred shifted towards Tc as the field was lowered, and coincided with the onset of diamagnetic screening of a small applied field. We associate this peak with the vortex melting transition. These results enabled us to study the phdynamic behavior of the phequilibrium melting transition in a range of low magnetic fields previously inaccessible.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1997
- Bibcode:
- 1997APS..MAR..K904S