Modification of the properties of GdBa₂Cu₃O_7-δ AND NdBa₂Cu₃O_7-δ by introduction of sulfur

The introduction of sulfur in the gadolinium based compound does not change the superconducting temperature T_c but increases the volume of the unit cell. For the noedymium compounds, the presence of sulfur depresses T_c and causes the crystal structure to change from orthorhombic to tetragonal. Furthermore, the Néel temperature characterizing the magnetic ordering of gadolinium spin changes slightly by introduction of sulfur. The nature of this antiferromagnetic order is discussed.