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Ac susceptibility in YBa2(Cu1-xFex)3O7-δ: Evidence for two-step irreversibility-line crossover

par Mehbod, Mohammad ;Sergeenkov, Sergei;Ausloos, Marcel;Schroeder, Jeannot ;Dang, An
Référence Physical review. B, Condensed matter, 48, 1, page (483-486)
Publication Publié, 1993

Article révisé par les pairs

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Résumé :

The ac susceptibilities of YBa2(Cu1-xFex)3O7-δ polycrystals for 0≤x<0.05 have been measured as a function of temperature and magnetic-field strength. Two different types of behavior of the irreversibility line, Tm(H), obeying the law 1-Tm/Tc∼Hq have been found. One corresponds to pure Y-Ba-Cu-O (x=0) and shows the commonly observed change of the power exponent q from 2/3 to 1 with increasing field. For the iron-doped samples an additional unusual crossover from q=1 to q=4/3 is observed practically within the same field and temperature interval as for the undoped one. The obtained results are described via the critical-state model taking into account the modification of the Josephson medium for the iron-doped case. In contrast to the silver-doped case [S.L. Shinde et al., Phys. Rev. B 41, 8838 (1990)], the pinning-force densities turn out to be smaller for iron-doped Y-Ba-Cu-O as compared to the undoped sample, probably due to iron-induced creation of a weak-link network inside grains. © 1993 The American Physical Society.