1/8 problems in the La-, Bi- and Y-based cuprates and new anomalies in theoverdoped region of the La-based cuprate

Recent experimental work on the 1/8 problem by our group is reviewed not on ly in the La-based cuprate but also in the Bi- and Y-based ones. In the par tially Zn-substituted Bi2Sr2Ca1-xYx (Cu1-xZny)(2)O8+delta, we have found an omalous suppression of superconductivity at x = 0.30 - 0.35, where the hole concentration per Cu p similar to 1/8. Moreover, it has been revealed from the mu SR measurements that the Cu-spin fluctuations exhibit slowing-down behavior at low temperatures in these samples. These results are suggestive of the stripe correlations of holes and spins tending to be pinned by Zn a t p similar to 1/8 in the Bi-based cuprate as well as in the La-based cupra te. In Y1-xCaxBa2Cu3O7-delta, the 60 K plateau of T-c has been found not to be correlated with the oxygen content but to be interpreted as being due t o the suppression of superconductivity at p similar to 1/8. Accordingly, we conclude that the 1/8 problem is common to all high-T-c cuprates with the CuO2 plane. Moreover, we have found transport and T-c anomalies around x = 0.22 in La2-xSrxCu1-yMyO4 (M = Zn, Ga), suggesting a possibility that an or der of holes and/or spins is formed or fluctuates in these samples in the o verdoped region.