Abstract:

Electron-doped T’-R2CuO4 type superconductors have been studied by X-ray diffraction, neutron diffraction, Raman, XPS, FT-IR, XAS, inelastic neutron sacttering, AC and DC magnetic measurement, resistivity measurement, specific heat and TEP measurement. A model was proposed from these experements. When R3+ was substituted with Ce4+ in the parent insulator R2CuO4, a part of doped electrons entered into CuO2 plane, but the other part was localized in the vicinity of Nd (Ce) ions. AFM ordering temperature of Cu disappeares as the dopant concentration approaches that required for superconductivity (Ce=0.15). After annealing treatment in N2 atmosphere, the localized electrons in the vicinity of Nd (Ce) ions transfered to the CuO2 plane and became free elections, the concentration of charge carriers was large enough to create SC. Some questions are still not clear at the present. It is necessary to perform more experements.

Key words: Electron-doped Superconductors, Magnetic order, Specific heat, Thermoelectric power, Raman spectra