Muon-spin relaxation study of the spin correlations in the overdoped regime of electron-doped high- T c cuprate superconductors

In order to investigate the low-energy antiferromagnetic Cu-spin correlations and their relation to the superconductivity, we have performed muon-spin-relaxation (μSR) measurements using single crystals of the electron-doped high-Tc cuprate Pr1-xLaCexCuO4 in the overdoped regime. The μSR spectra have revealed that the Cu-spin correlations are developed in the overdoped samples where the superconductivity appears. The development of the Cu-spin correlations weakens with increasing x and is negligibly small in the heavily overdoped sample where the superconductivity almost disappears. Considering that the Cu-spin correlations also exist in the superconducting electron-doped cuprates in the undoped and underdoped regimes [T. Adachi, J. Phys. Soc. Jpn. 85, 114716 (2016)JUPSAU0031-901510.7566/JPSJ.85.114716], our findings suggest that the mechanism of the superconductivity is related to the low-energy Cu-spin correlations in the entire doping regime of the electron-doped cuprates.