The hysteresis loop of internal friction associated with magnetic flux pinning in YBa2Cu3O7-xsuperconductors

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Abstract
The hysteresis loops of internal friction associated with the magnetic flux pinning in high-Tc bulk and film YBa2Cu3O7-x superconductors were investigated by the vibrating-reed technique. When a cyclic magnetic field is applied, both the internal friction QB-1 and the resonant frequency fr exhibit a hysteresis loop. This is explained on the basis of the Bean model. It is considered that the variation in the QB-1 hysteresis loop reflects the different mobilities of the flux lines at different positions of the pinning potential well. The critical current density Jc and the bulk pinning force density Pv were estimated from the QB-1 hysteresis loop for the film specimen.