Mössbauer study of 1/8 anomaly in La2−x Ba x CuO4
The measurements of Mössbauer effect, magnetic susceptibility and muon spin relaxation have been carried out for the high-T c superconductor La2−x Ba x CuO4. The intensity of Mössbauer doublet spectrum of the sample of x∼1/8 begins to decrease rapidly at a certain temperature T m, which we define as a magnetic transition temperature T Möss. This temperature almost agrees with T μSR determined from muon spin relaxation. The quadrupole doublet disappears at low temperature below T m but a clearly splitted spectrum is not observed even at 4.2 K, which indicates a peculiar magnetic state with a wide distribution of internal magnetic field. Around x∼1/8, the superconducting critical temperature T c and T m are competed each other. In conclusion, superconductivity disappears around 1/8 hole concentration and a peculiar magnetic state such as spin density wave appears.
Key wordshigh-Tc superconductor 1/8 anomaly
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