STUDY ON SULFUR DOPING OF THE LA2-YMYCUO4 (M = SR AND BA) SYSTEM

Superconducting transition temperatures T(c) and Hall coefficients R(H) of La2-yMyCuO4-xSx (M = Sr and Ba) have been measured for various values of x and y. The T(c) versus (y-x) curve of the system is found to be almost identical to the T(c) versus y curve of the La2-yMyCuO4 system. The well-known T(c)-depression in La2-yMyCuO4 found at y = 1/8 also exists in the present system at y-x congruent-to 1/8. All the obtained data are consistent with the idea that through the doping of every two S atoms, three O atoms are expelled from the LaO planes, which results in the creation of one oxygen vacancy site. Even this strong randomness caused by the S doping does not change the value of T(c), in the sense that T(c) of La2-yMyCuO4-xSx is equal to that of La2-uMuCuO4 with u=y-x or with equal hole concentration.