Superconducting phase diagram of electron-doped cuprates Nd2$minus;xCexCuO4

Detailed superconducting (SC) phase diagram of electron-doped cuprates Nd2−xCexCuO4 has been studied by magnetic susceptibility measurements on single crystals with Ce concentration x up to 0.17. On increasing x, fractional superconductivity appears at around x=0.075. On further doping, bulk superconductivity sets in at around x=0.135, where the volume fraction of antiferromagnetic phase drastically degrades. SC samples with different onset Tc∼20 and 25 K were prepared by heat treatment in both fractional and bulk SC phases at a fixed x, and there exists no region where the onset Tc depends on doping in the studied x-region. The boundary between fractional and bulk SC phases slightly shifts depending on the conditions of heat treatment.