1/8 anomaly in the excess-oxygen-doped La_2-xA_xCuO_4+δ (A = Nd, Bi, Pr)

We have investigated in detail dependence on p (the hole concentration per Cu) of the transport properties and T_c in the excess-oxygen-doped La_2-xA_xCuO_4+δ (A = Nd, Bi, Pr), where the phase separation of the excess oxygen is suppressed. The so-called 1/8 anomaly has been found in La_1.8Nd_0.2 CuO_4+δ. The 1/8 anomaly has become marked through the 1% substitution of Zn for Cu. The μSR measurements have revealed that the magnetic correlation develops at low temperatures below about 40 K in both Zn-free and 1% Zn-substituted samples with p = 1/8 and that a long-range magnetic order is formed below 1 K in the 1% Zn-substituted sample with p = 1/8. These results support the stripe-pinning model. Neither La_2-xBi_xCuO_4+δ nor La_2-xPr_xCuO_4+δ has exhibited the clear 1/8 anomaly.