The irreversible properties of a rare-earth high-T-c superconductor are investigated using grain-aligned Sm1-xEuxBa2Cu3O7-delta (x = 0.0, 0.3, 0.5, 0.7, and 0.9) samples. The samples were synthesized using the usual solid-state reaction method. It is found that the transition temperature T-c and the critical current density J(c) calculated by the Bean model are significantly improved in the optimally doped samples (x = 0.5 and 0.7). Furthermore, the double logarithmic graph of the irreversibility line B-irr in the grain-aligned series samples obeys approximately a power law dependence (1 - T/T-c)(n). Results show that in the case of optimally doped samples with x = 0.5 and 0.7 the graph of B-irr is fitted well with the relation (1 - T/T-c)(n) with the model-dependent parameter n similar to 1.5 without any crossover in the entire temperature range, while in samples with x = 0.0, 0.3, and 0.9 B-irr does show a prominent crossover and can be characterized with n similar to 1.5 only near T-c, above which B-irr varies more rapidly. Finally, it is suggested that B-irr is strongly dependent on the extrinsic properties of our grain-aligned samples. (C) 2010 Elsevier B.V. All rights reserved.