A CALORIMETRIC STUDY OF LONG-RANGE AND SHORT-RANGE MAGNETIC-INTERACTIONS OF THE R(3+) IONS IN NDBA2CU3OX AND DYBA2CU3OX

Low temperature specific heat measurements were performed in order to obtain information about the magnetic ordering effects in NdBa2Cu3Ox (Nd123x) and DyBa2Cu3Ox (Dy123x). In the specific heat of both system a strong oxygen dependence was observed. While for Nd123x the shape and the position of the specific heat anomaly is changed by changing the oxygen content, for Dy123x only a change in the shape was measured. A shift in the position indicates a variation in the magnetic coupling, whereas the observed changes in shape are a result of variations in the magnetic correlation length.