Comparative study of magnetic behavior of RuSr2RE1.5Ce0.5Cu2O10-δ where RE=Eu and Sm

Systematic investigation of structural, magnetic and transport properties of RuSr2RE2-xCexCu2O10 with RE being Sm and Eu has been performed. We present the experimental evidence that the synthesis of RuSr2Eu1.5Ce0.5Cu2O10 under non-optimised heat treatment conditions may results in the formation of secondary RuSr2EuCu2O8 phase. In contrast, similar preparation conditions for RuSr2Sm1.5Ce0.5Cu2O10 samples lead to the pure phase. Consequently, RuSr2Eu1.5Ce0.5Cu2O10 samples exhibit a small peak around 125 K in the temperature dependence of dc magnetization, pronounced irreversibility between zero-field cooled and field cooled curves at temperatures higher than the peak temperature, and the bell shaped behavior of the coercive field as the function of temperature above Curie's temperature. These anomalous features, which may arise due to the superposition effect of the main and secondary phases, which are both magnetic, are completely absent for RuSr2Sm1.5Ce0.5Cu2O10 sample, which does not consist of the secondary phase.