Muon spin relaxation study of the Cu spin dynamics in electron-doped high- Tc superconductor Pr_0.86 LaCe_0.14 Cu_1-y Zn _yO₄

Muon-spin-relaxation (μSR) measurements have been performed for the partially Zn-substituted electron-doped high- Tc 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 Pr3⁺ 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 Pr3⁺ 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_x Cu_1-y Zn_y O ₄. The possible reason may be that there are no dynamical stripe correlations of spins and electrons in the electron-doped high- Tc cuprates or that the effect of Pr3⁺ moments on the μSR spectra is stronger than that of a small amount of Zn impurities.