The modulation of the peak effect in melt-processed (Sm-Eu)123 superconductors with compositional fluctuations

The peak effect in magnetization loops of melt-processed (Sm/sub x/Eu/sub 1-x/)Ba/sub 2/Cu/sub 3/O/sub 7-(delta)/ superconductors is manipulated by varying the Sm/Eu ratio in the initial composition. In all the samples the peak field B/sub p/(T), at which the magnetization moment reaches the maximum, was linearly temperature dependent. The fitting to such a relationship unveils a slightly lower critical temperature T/sub cp/ than the bulk T/sub c/ at zero field. A kink appears in the reversible magnetization moment of the field dependence of superconducting transition. This kink temperature T/sub ck/(B) is also a linear function of applied field. Transmission electron microscopy (TEM) observation confirms the presence of nano-scale regular compositional modulation arising from local RE-Ba substitution, which is weakened with increasing Eu concentration. The peak effect is thus attributed to the scattering of local T/sub c/ due to compositional fluctuation.