Magnetic relaxation in Tl2Ba2CaCu2O8 single crystals by SQUID magnetometer and micro-Hall sensor
P. Chowdhury, Heon-Jung Kim, W. N. Kang, Dong-Jin Zang, Sung-Ik Lee, D. H. Kim
DOI 10.1103/PhysRevB.68.134413 · Physical Review B
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Abstract
Measurements of the isothermal magnetization hysteresis loops M(H) and the magnetic relaxation for a Tl2Ba2CaCu2O8 single crystal were carried out by using a superconducting quantum interference device magnetometer and a micro-Hall sensor. In the temperature window from 30 to 60 K, the measurements for M(H) show a second anomalous peak at a field Hsp and an onset field of Hon. From these relaxation data measured by two different techniques, the activation barrier U0 and the creep exponent μ were separately calculated as functions of H based on the weak collective pinning theory. The variation of the normalized creep rate, S=(|dlnM/dlnt|), with H is also presented. The results at T=35K indicate that at a characteristic field H* lying between Hon and Hsp, a minimum is observed in S(H) whereas a maximum is observed in U0(H). These analyses also show that below H*, the creep phenomenon is controlled by an elastic process. However, above Hsp a negative power law, U0(H)∝Hν with ν∼−0.9, is observed suggesting the existence of plastic creep. At a low temperature of T=20K, where no second peak is observed, both S(H) and U0(H) behave differently. A comparative study of the different creep parameters obtained from the two different measurement techniques is also discussed.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Tl2Ba2CaCu2O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 105 | Pressure not reported | onset |
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