Effects of Pr, Tb, and Zn doping into YBa2Cu3O7 on magnetoresistivity and magnetic phase boundaries

Transverse AB-plane magnetoresistivity rho(AB) (C axis l\H) of (Y1-xPrx)Ba2Cu3O7-delta and YBa2(Cu1-xZnx)(3)O-7-delta thin films and (Y1-xTbx)Ba2Cu3O7-delta thin films and single crystals has been measured as a function of 0.0 < X <X(C), 2 K < T < 300 K, and 0 T < H < 20 T. Mean-field upper critical field H-C2 and irreversibility field H(I)irreversibility field HI phase boundaries have been determined and are discussed in terms of proposed theories. Tb doping of YBa2Cu3O7 reflects an enhanced pinning or ''stiffening'' of the vortex system without apparent alteration to T-C or the slope of the mean-field normal phase-mixed phase boundary line, dH(C2)/dT/T=T-c. However, Pr and Zn doping of YBa2Cu3O7 tends to depress both T-C and dH(C2)/dT/(T=Tc) and shows a ''softening'' of the vortex system. This behavior may be understood in terms of the magnitude of the superconducting pair coherence length, which is controlled by doping, and the divergence of the vortex-glass correlation length as it relates to flux line coupling of vortices in the CuO2 places. These systems are compared with other high T-C superconducting systems which possess similar phase boundary properties. (C) 1996 American Institute of Physics.