| Emergence of a Novel Frozen Magnetic State in a Heavily Overdoped Non-Superconducting Copper Oxide (2009) | |||||||||
Abstract | |||||||||
| The doping of charge carriers into the CuO2 planes of copper oxide Mott insulators causes a gradual destruction of antiferromagnetism and the emergence of high-temperature superconductivity. Optimal superconductivity is achieved at a doping concentration p beyond which further increases in doping cause a weakening and eventual disappearance of superconductivity. One explanation for this demise is that ferromagnetic fluctuations compete with superconductivity in the overdoped regime. In this case a ferromagnetic phase at very low temperatures is predicted to exist beyond the doping concentration at which superconductivity disappears. Here we report on a direct examination of this scenario in overdoped La2-xSrxCuO4 using the technique of muon spin relaxation. We detect the onset of static magnetic moments of electronic origin at low temperature in the heavily overdoped non-superconducting region, where antiferromagnetic correlations are absent. However, the magnetism is found not to exist in a commensurate long-range ordered state. Instead it appears as a dilute concentration of static magnetic moments, consistent with the prediction from electronic band calculations of weak ferromagnetic order about Sr-rich clusters. The superconducting phase of copper oxides is thus sandwiched between magnetic phases that compete with superconductivity.. Comment: 20 pages, 5 figures | |||||||||
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