The Underdoped Region of the Phase Diagram of YBa2Cu3O6+x

Here we present a reviewed phase diagram of the high-T c superconducting YBa2Cu3O6+ x compound, finely mapped in the strongly underdoped region (0<x<0.5), from the pure antiferromagnetic state to the superconducting regime. The Neèl and spin freezing temperatures have been measured by μSR experiments while the hole density per Cu atom in the CuO2 planes has been determined from the resistive T c and from Seebeck coefficients at 290 K. The phase diagram is discussed in comparison to those of La2− x Sr x CuO4 and Y1− x Ca x Ba2Cu3O6 cuprate systems