  Zero-field muon-spin-relaxation measurements have been carried out in order
to investigate the Zn- and Ni-substitution effects on the Cu-spin dynamics in
the electron-doped Pr_0.86_LaCe_0.14_Cu_1-y_(Zn, Ni)_y_O_4+\alpa-\delta_ with y
= 0, 0.01, 0.02, 0.05 and different values of the reduced oxygen content
\delta(\delta \le 0.09). For the samples with y = 0 and very small \delta
values of \delta < 0.01, a muon-spin precession due to the formation of a
long-range antiferromagnetic order has been observed at low temperatures below
\~ 5 K. For the moderately oxygen-reduced samples of 0.01 \le \delta \le 0.09,
on the contrary, no muon-spin precession has been observed and the temperature
dependence of the spectra is similar to one another regardless of the y value.
That is, no impurity-induced slowing down of the Cu-spin fluctuations has been
detected, which is very different from the results of the hole-doped high-T_c_
cuprates. The reason is discussed.
