Nonlinear ac response of the vortex system in the cubic (K, Ba)BiO3 superconductor

A. Conde-Gallardo; I. Joumard; J. Marcus; T. Klein

doi:10.1007/s100510050936

EPJ

Nonlinear ac response of the vortex system in the cubic (K, Ba)BiO₃ superconductor

A. Conde-Gallardo¹^,2, I. Joumard¹, J. Marcus¹ and T. Klein¹^a

¹ Laboratoire d'Études des Propriétés Électroniques des Solides, Centre National de la Recherche Scientifique, B.P. 166, 38042 Grenoble Cedex 9, France
² Departemento de Fisica, CINVESTAV-IPN, Apdo, Postal 14-740, Mexico D.F. 07300, Mexico

Received: 17 March 1999
Published online: 15 September 1999

Abstract

We present ac susceptibility measurements performed on $\rm (K,Ba)BiO_3$ single crystals with different geometries: thick films, bars and hollow cylinders. We show that the h_ac dependence of the real ( $\chi '$ ) and imaginary ( $\chi ^\prime$ ) parts of the ac susceptibility is in very good agreement with Brandt's numerical calculations (Phys. Rev. B 58, 6523 (1998)) in the modified Bean critical state. Creep effects (at $H_{\rm dc} = 0.3T$ ) are investigated by studying the frequency dependence of the current density deduced from the temperature scans of the ac susceptibility over a large frequency range ( $0.02 {\rm Hz} < \omega < 2000 {\rm Hz}$ ). The relaxation rate $S = {\rm dln}(J)/{\rm dln}(\omega) \sim 4\%$ is temperature independent and very similar to the one usually obtained in high T_c cuprates.

PACS: 74.60.Ge – Flux pinning, flux creep, and flux-line lattice dynamics / 74.60.Ec – Mixed state, critical fields, and surface sheath / 74.25.Nf – Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.)

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EPJ

Nonlinear ac response of the vortex system in the cubic (K, Ba)BiO3 superconductor

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Nonlinear ac response of the vortex system in the cubic (K, Ba)BiO₃ superconductor