EFFECTS OF THE CU-SITE SUBSTITUTION ON THE ANOMALOUS X-DEPENDENCE OF TC IN LA2-XBAXCUO4

Effects of the partial substitution of Ni, Zn and Ga for Cu on the anomalous x dependence of T(c) and the resistance anomaly around 60 K have been investigated in La2-xBa(x)CuO4. T(c) decreases by the substitution in comparison with non-substituted samples in almost all compositions of x except compositions near x = 0.125. For 1% Ga-substituted samples for Cu, the local minimum of T(c) as a function of x, appearing near x = 0.125 for non-substituted samples, clearly shifts to x almost-equal-to 0.135. This suggests that the low-temperature structural phase transition around x = 0.125 in La(2-x)Ba(x)CuO4 is primarily due to the optimum hole concentration of 0.125 per Cu atom rather than the atomic ordering of La and Ba. The resistance anomaly near 60 K does not change clearly by the substitution.