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Type: Artigo de periódico
Title: Experimental verification for a scaling law relating amplitude and frequency in the complex susceptibility of type-II superconductors
Author: Cardoso, CA
de Lima, OF
Abstract: In this work we present complex susceptibility measurements chi(h,v), for a large range of field amplitudes h and frequencies v, taken in two Nb samples (one single crystal and one polycrystal) and one melt-textured YBa2Cu3O7-delta sample. A predicted scaling law for chi(h,v) is verified for several sets of data, plotted against the scaling variable h(v(ref)/v)(1/(n-1)), where v(ref) is an arbitrary reference frequency and n is a creep exponent. Data taken closer to T-c revealed a useful scaling applied directly to the critical current density J(c), evaluated through the peak position of the imaginary component chi '. An unexpected frequency dependence of n was observed for the YBa2Cu3O7-delta sample. This is associated with a failure of the logarithmic approximation for the activation energy U = U(c)ln(J(c)/J), which is assumed in the scaling formalism. A more accurate description in this case is obtained with U = U-c(J/J(c))(-mu), from the collective creep theory. This type of analysis led us to propose an effective creep exponent n(eff), in an attempt to keep the original scaling law. (C) 2000 Elsevier Science B.V. All rights reserved.
Subject: complex susceptibility
AC susceptibility scaling
nonlinear ac response
collective flux creep
Country: Holanda
Editor: Elsevier Science Bv
Rights: fechado
Identifier DOI: 10.1016/S0921-4534(00)00265-3
Date Issue: 2000
Appears in Collections:Unicamp - Artigos e Outros Documentos

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