Temperature dependence of the peak effect in NdBa₂Cu ₃O _7-δ single crystals and melt-processed (Sm _0.5Eu_0.5)Ba₂Cu₃O _7-δ single domains

Magnetization loops of NdBa₂Cu₃O_7-δ (Nd123) single crystals grown under low oxygen partial pressure and melt-processed (Sm_0.5Eu_0.5)Ba₂Cu ₃O_7-δ (SE123) crystals with post-annealing in Ar were comparatively studied in a wide temperature and field regime. The peak field at which magnetic moment displays the maximum, exhibits a linear temperature dependence in both cases. The fitting shows a slightly lower critical temperature than bulk T_c at null applied field. The temperature dependence of the onset field from which the absolute value of magnetic moment starts to increase, indicates the dominant pinning at low fields in Nd123 single crystals is the surface barrier while the RE211/123 interfacial pinning in melt-processed SE123 crystals.