Implications of the isotope effects on the magnetization, magnetic   torque and susceptibility
  We analyze the magnetization, magnetic torque and susceptibility data of La2-xSrxCu(16,18)O4 and YBa2(63,65)CuO7-x near Tc in terms of the universal 3D-XY scaling relations. It is shown that the isotope effect on Tc mirrors that on the anisotropy. Invoking the generic behavior of the anisotropy the doping dependence of the isotope effects on the critical properties, including Tc, correlation lengths and magnetic penetration depths are traced back to a change of the mobile carrier concentration. 
T. Schneider