Muon spin relaxation study of the Cu spin dynamics in electron-doped high-T_c superconductor Pr_(0.86)LaCe_(0.14)Cu_(1-y)Zn_yO_4

摘要

Muon-spin-relaxation (μSR) measurements have been performed for the partially Zn-substituted electron-doped high-T_c superconductor Pr_(0.86)LaCe_(0.14)Cu_(1-y)Zn_yO_(4+α-δ) with y=0-0.05 and the reduced oxygen content δ=0-0.09, in order to investigate nonmagnetic Zn-impurity effects on the Cu-spin dynamics. For all the measured samples with 0.01 ≤ δ≤0.09, it has been found that a fast depolarization of muon spins is observed below 100 K due to the effect of Pr~(3+) moments and that the μSR time spectrum in the long-time region above 5 μsec increases with decreasing temperature at low temperatures below 30 K possibly due to slowing down of the Cu-spin fluctuations assisted by Pr~(3+) moments. No Zn-induced slowing down of the Cu-spin fluctuations has been observed for moderately oxygen-reduced samples with 0.04 ≤δ≤0.09, which is very different from the μSR results of La_(2-x)Sr_xCu_(1-y)Zn_yO_4. The possible reason may be that there are no dynamical stripe correlations of spins and electrons in the electron-doped high-T_c cuprates or that the effect of Pr~(3+) moments on the μSR spectra is stronger than that of a small amount of Zn impurities.