Suppression of Pseudogap Behavior and Antiferromagnetic Fluctuations by Electron Doping in T′-La1.8Eu0.2CuO4−yFy Studied by 63,65Cu NMR

We performed 63,65Cu NMR measurements of an electron-doped high-Tc cuprate superconductor T′-La1.8Eu0.2CuO4−yFy (0 ≤ y ≤ 0.125) having Nd2CuO4-type structure (so-called T′-structure). Pseudogap behavior is observed in the lightly electron-doped region of y ≤ 0.075. The nuclear spin–lattice relaxation rate 1/T1 revealed that the antiferromagnetic spin fluctuations are suppressed by electron doping. These behaviors are like those reported in the optimum- and over-doped region of hole-doped high-Tc cuprate superconductors. It appears that electrons are more effectively doped through partial substitution in T′-La1.8Eu0.2CuO4−yFy than in isostructural T′-Pr1.7−xLa0.7CexCuO4.