ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Magnetization-vector measurements were made at various temperatures on polycrystalline disks of YBa2Cu3O7 and (Ba,K)BiO3 as each was rotated about its axis in a fixed field H along the disk plane. For hysteretic starting states, the vortex flux density vector B is found to bifurcate into a BR component that rotates rigidly with the sample and a BF component that stays at a fixed angle (θF) relative to H, thus turning frictionally relative to the sample, as seen earlier. With increasing H, BR decreases and BF increases in size, indicating a distribution in the strength of the vortex pinning torques. After BR has vanished, the frictional angle θF decreases rapidly. Thus, the quantity Hμ sin θF (μ being the quantized vortex moment), which equals the average pinning torque (τp) on each vortex, does not remain constant but diminishes with increasing H. This decrease of τp is consistent with the collective pinning phenomenon known as vortex bundling. At fixed H, τp diminishes rapidly with increasing temperature, reaching very low values well below Tc. These results are compared with those derived from critical-state model interpretations of conventional hysteresis loop data. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.362159
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