Multiple Magnetic Transitions in RuSr₂R_1.4Ce_0.6Cu₂O₁₀ (R = Gd, Eu) from Magnetization and ESR Spectroscopy

Abstract

We studied magnetization and ESR on RuSr₂R_1.4Ce_0.6Cu₂O₁₀ (Ru1222; R = Gd, Eu). A ferromagnetic hysteresis in M–H curves is observed below T_M=180 K. The saturation moment is smaller than that for the expected Ru⁵⁺. These results suggest that Ru1222 is weak ferromagnetic. Interestingly, an enhancement in M observed at 100 K is more substantial than that observed at T_M. ESR measurements confirm that this anomalous behavior originates from a change in the Ru moment.