Magnetic Ground State of Pr${}_{0.89}$LaCe${}_{0.11}$CuO${}_{4+\alpha -\delta }$ with Varied Oxygen Depletion Probed by Muon Spin Relaxation

The magnetic ground state of an electron-doped cuprate superconductor Pr${}_{1-x}$LaCe${}_x$CuO${}_{4+\alpha -\delta }$ ($x=0.11,\alpha \simeq 0.04$) has been studied by means of muon spin rotation/relaxation (\msr) over a wide variety of oxygen depletion, $0.03\le \delta \le 0.12$. Appearance of weak random magnetism over entire crystal volume has been revealed by a slow exponential relaxation. The absence of $\delta$-dependence for the random magnetism and the multiplet pattern of muon Knight shift at higher fields strongly suggest that the random moments are associated with excited Pr${}^{3+}$ ions under crystal electric field.