Published online by Cambridge University Press: 28 February 2011
Samples of the composition MBa2Cu3O7−x with M = Y, Eu, Er, and Gd have been prepared by the standard solid state reaction method. The magnetic susceptibility has been investigated above room temperature up to 187O K in vacuum. Specific heat measurements have been performed with a differential scanning calorimeter (DSC) working at low temperatures in a differential mode using superconducting and non-superconducting samples. The surface topography of the high-Tc superconductors has been investigated at room temperature by scanning tunneling microscopy (STM).