Possibility of an ordered state of spins and holes in single-crystal La_2-xSr_xCu_1-yZn_yO₄ (x = 0.21, y = 0 and 0.01) studied by μSR

Zero-field (ZF) and longitudinal-field (LF) muon spin relaxation (μSR) measurements have been carried out in the overdoped single crystals of La_2-xSr_xCu_1-yZn_yO₄ with x = 0.21, y = 0 and 0.01. In the case of the Zn-substituted crystal with x = 0.21 and y = 0.01 in which the high-T_c superconductivity is almost suppressed, the ZF- and LF-μSR measurements have revealed the existence of a static ordered state of Cu spins at low temperatures below 2 K. No clear coherent precession of the muon spin has been observed down to 20 mK. Slowing down of the Cu-spin fluctuations has also been observed in the non-Zn-substituted crystal with x = 0.21 and y = 0 at low temperatures below about 0.8 K in ZF, indicating that the observed magnetic anomaly is an intrinsic property at x = 0.21. These μSR results suggest a strong possibility of the existence of a spin/charge ordered state at x = 0.21 in the overdoped region.