Factors affecting a characteristic flux pinning in light rare earth (RE)-Ba-Cu-O (RE: Nd, Sm, Eu, Gd) superconductors fabricated by the oxygen-controlled-melt-growth (OCMG) process have been investigated through a comparative study. At 77K and for the applied field parallel to the c-axis of the sample (H//c), the flux pinning of all OCMG-processed REBa2Cu3O (RE123) samples studied was very sensitive to the oxygen partial pressure (PO2) controlled during the melt growth and thus, with lowering PO2, the peak field (Bpk) in the M-H loops shifted to a high field and the irreversibility line (IL) shifted to a high H-T region. For a Ndl23 sample, as the oxygen annealing temperature increased above 300‡C, both Bpk and IL were systematically depressed. However, Bpk for all systems was insensitive to the amount of the second phase (Nd4Ba2Cu2O10 (Nd422) and RE2BaCuO5 (RE211) for the other) inclusion in the superconducting RE123 matrix, supporting that the characteristic flux pinning is due to the superconducting matrix.
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