Structural change and superconductivity in La_(1.85-2x)Sr_(2x+0.15)Cu_(1-x)Ru_xO_4 and La_(1.85)Sr_(0.15)Cu_(1-x)Ru_xO_4 systems

摘要

The structural changes and superconductivity of La_(1.85-2x)Sr_(2x+0.15)Cu_(1-x)Ru_xO_4 (I) and La_(1.85)Sr_(0.15)Cu_(1-x)Ru_xO_4 (II) systems have been investigated. It was observed that the Ru doping strongly suppresses T_c. The critical contents x_c for T_c disappearances are respectively 0.0225 and 0.019 for the (I) and (II) systems. It was found that in all La_(1.85)Sr_(0.15)Cu_(1-x)M_xO_4 systems investigated (M = Ru, Li, V, Sn, Al, Ga, Co, Fe, Mn, Mg, Ni and Zn), the structure parameter c/a ratios decrease with increasing doping content x, which is a common characteristic. The mechanisms for T_c suppression in the La_(1.85)Sr_(0.15)CuO_4 system are summarized and discussed briefly.