Phase diagram moved to overdoped region in La2−xSrxCu0.94Ti0.06O4 system

The magnetization, electronic resistivity, infrared (IR) transmission, and Raman scattering measurements have been carried out in La2−xSrxCu0.94Ti0.06O4 (0.15≤x≤0.39) samples in which the superconductivity has entirely vanished as x=0.15 and 6% Ti substitution for Cu. The reappearance of superconductivity in La2−xSrxCu0.94Ti0.06O4 system is observed when increasing x (>0.15). A new phase diagram of superconductivity for La2−xSrxCu0.94Ti0.06O4 is plotted, and the whole phase diagram moves to the over-doped region compared with the phase diagram of La2−xSrxCuO4. The results can be understood in terms of a compensation effect of charge carriers arising from the local electrons induced by the doping of Ti compensated by the holes introduced through Sr doping as evidenced by the spectra of IR and Raman scattering.