Multiple peaks in the ac susceptibility of untwinned Y-Ba-Cu-O single crystals: A manifestation of the peak effect
Date
1994Source
Physical Review BVolume
50Pages
16001-16007Google Scholar check
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We have measured the ac susceptibility of several high quality twinned and detwinned YBa2Cu3O7- (YBCO) single crystals. We see multiple peaks in the (T) curves, and explain them as a manifestation of the peak effect in Jc(T) near Tc and increased Jc at low temperatures. We have investigated the effect of electron irradiation on these peaks, and found that it increases Jc of the sample. We suggest that the narrow, high-temperature (just below Tc) peak in (T) is an indication that the sample is clean, and therefore exhibits a first-order melting transition of the flux-line lattice. We also propose that the peak effect in Jc is a result of the softening of the lattice before it melts, in accordance with Pippards model of this phenomenon for low-temperature superconductors. Finally, we suggest a method of determining the true irreversibility line. © 1994 The American Physical Society.