Low-energy spin fluctuations in the ground states of electron-doped Pr1-x LaCexCuO4+delta cuprate superconductors.

Low-energy spin fluctuations have been investigated in the electron-doped Pr{1-x}LaCe{x}CuO{4+delta} over a wide concentration range of 0.07<or=x<or=0.18, spanning from the antiferromagnetic phase to the heavily overdoped superconducting (SC) phase. The low-energy excitations exhibit commensurate peaks centered at the (pi, pi) position for all x. Our data show that the characteristics of the excitations, such as the relaxation rate and the spin stiffness, decrease with increasing x in the SC phase and disappear with the disappearance of superconductivity.