Electron-Doping Effect on T-c in the Undoped (Ce-Free) Superconductor T'-La1.8Eu0.2CuO4 Studied by the Fluorine Substitution for Oxygen

摘要

We have succeeded in synthesizing electron-doped polycrystalline bulk samples of T'-La1.8Eu0.2CuO4-yFy (y = 0-0.15) by the fluorination of undoped (Ce-free) T'-La1.8Eu0.2CuO4 using NH4F. The magnetic susceptibility measurements have revealed that the superconducting transition temperature, T-c, increases with increasing y, exhibits the maximum of 23 K at y = 0.025, and decreases. The dome-like dependence of T-c on the doped carrier concentration in the TA-type (La,Eu)-based cuprates is explained in terms of the pairing mediated by spin fluctuations based on the d-p model calculation