Magnetic Field Effect on the Superconducting Transition in (RE)xBa1-xCuOy

Koike, Yasuhiro; Nakanomyo, T.; Hanaguri, T.; Nomoto, T.; Fukase, Tetsuo

doi:10.1143/jjap.26.l2069

Cited by 6 publications

References 19 publications

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Dynamical critical fields, aging effects, and restoring in some YBa2Cu3Ox compounds studied by complex susceptibility measurements

Mehdaoui

Bolmont

Loegel

1989

Phys. Stat. Sol. (a)

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The ac initial complex susceptibility of sintered samples of high temperature superconducting YBaCuO compounds is studied in detail. The importance of using very low external magnetic ac fields (ha, < Oe) is pointed out in order to prevent dynamical saturation (flux-pinning) when reaching the critical ac field 7$ which is much lower than the first critical (static) field H c l . The field, temperature, and frequency dependences of both real part (diamagnetic shielding) and imaginary part (power losses) are consistent with a rather large spread of critical temperatures over the volume: the highest (T, = 90 K) a t the surface and the lowest (50 < T , < 80 K) in the inner part of the volume. It is also shown that this technique is a very useful tool for studying and/or controlling aging effects, water contamination, and thermal restoring treatments.Nous avons Btudie en details la susceptibilite alternative en champs faibles de quelques composes frittBs du type YBaCuO. Nous demontrons l'importance de I'emploi de champs magnetiques extremement faibles (ha, < low3 Oe) afin d'eviter des ph6nomi.nes de saturation dynamique (ancrage des vortex) lors que l'on atteint le champ dynamique critique qui est nettement plus faible que le premier champ critique (statique) H,1. L'Bvolution des parties reelle et imaginaire de la susceptibilite en fonction de la temperature, de la frequence et du champ magnetique sont en accord avec I'existence d'une distribution en volume des temperatures critiques: les temperatures les plus 61evBes (T, = 90 K) correspondant B la surface 0t les temperatures les plus basses (50 < < T , < 80 K) correspondant iL I'interieur du volume. La susceptibilite alternative en champs faibles apparait comme Atant un outil extr6mement utile pour ]'etude et/ou le controle des effets du vieillissement, de la contamination par la vapeur d'eau et des traitements thermiques.

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