Dynamic regimes in the ac response of YBa2Cu3O7 with columnar defects: Intra- and inter-valley vortex motion

G. Pasquini, L. Civale, H. Lanza, and G. Nieva
Phys. Rev. B 59, 9627 – Published 1 April 1999
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Abstract

We use ac susceptibility measurements to explore the dynamic response of vortices in YBCO single crystals pinned by aligned columnar defects at low dc fields. Using a combination of techniques for the analysis of the data, we investigate the vortex motion as a function of the amplitude and frequency of the applied ac field hac, identifying the influence of both intra- and inter-valley motion. We build up a dynamic diagram in the hacT plane indicating the crossover lines among several regimes in the solid phase. At low hac, a linear response with very low dissipation arises from the oscillation of pinned vortices inside the tracks (Campbell regime). At high hac a critical state develops. The large influence of thermal fluctuations in this limit is indicated by the frequency dependence, which allows us to obtain the current density dependence of the activation energy and the glassy exponent. We also discuss the origin of the large nonlinear transition regime observed at intermediate amplitudes.

  • Received 1 December 1997

DOI:https://doi.org/10.1103/PhysRevB.59.9627

©1999 American Physical Society

Authors & Affiliations

G. Pasquini

  • Comisión Nacional de Energía Atómica–Departamento de Física, Av. del Libertador 8250, 1429, Buenos Aires, Argentina

L. Civale

  • Comisión Nacional de Energía Atómica–Centro Atómico Bariloche and Instituto Balseiro–CNEA, 8400 Bariloche, Argentina

H. Lanza

  • Comisión Nacional de Energía Atómica–Departamento de Física, Av. del Libertador 8250, 1429, Buenos Aires, Argentina

G. Nieva

  • Comisión Nacional de Energía Atómica–Centro Atómico Bariloche and Instituto Balseiro–CNEA, 8400 Bariloche, Argentina

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Vol. 59, Iss. 14 — 1 April 1999

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