The temperature dependences of the third harmonics of the AC susceptibility, χ3′(T) and χ3″(T), have been used to study the vortex dynamics in Melt Textured YBCO. The experimental curves measured at different AC field amplitudes and frequencies, have been compared with the simulations of χ3′(T) and χ3″(T) obtained by considering the diffusion of the magnetic flux in the presence of different dynamic regimes. The comparison made as function of the AC field frequency shows that, at low frequencies, the magnetic response is mainly described in terms of a Bean critical state model. As the frequency is increased, the contributions coming from the flux dynamic regimes become predominant. Nevertheless, at the highest frequencies, contrary to what was expected, the curves appear again very similar to the ones simulated in terms of a pure Bean critical state model.

Flux Dynamics and Critical State in YBCO by AC Harmonic Susceptibility

POLICHETTI, Massimiliano;VECCHIONE, ANTONIO;PACE, Sandro
2000-01-01

Abstract

The temperature dependences of the third harmonics of the AC susceptibility, χ3′(T) and χ3″(T), have been used to study the vortex dynamics in Melt Textured YBCO. The experimental curves measured at different AC field amplitudes and frequencies, have been compared with the simulations of χ3′(T) and χ3″(T) obtained by considering the diffusion of the magnetic flux in the presence of different dynamic regimes. The comparison made as function of the AC field frequency shows that, at low frequencies, the magnetic response is mainly described in terms of a Bean critical state model. As the frequency is increased, the contributions coming from the flux dynamic regimes become predominant. Nevertheless, at the highest frequencies, contrary to what was expected, the curves appear again very similar to the ones simulated in terms of a pure Bean critical state model.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/3744277
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