STUDY OF THE STRUCTURAL PHASE-TRANSITION IN GD2-XCEXCUO4

The structural phase transition in Gd2-xCexCuO4 (x = 0, 0.12) characte rized by the rotation of the CuO4-squares around the c axis has been s tudied by different diffraction techniques. The order parameter of thi s transition is found to increase continuously below 658(1) K for Gd2C uO4 and below 707.2(7)K for Gd1.88Ce.12CuO4 with an unusual temperatur e dependence, The rotation of the CuO4-squares is coupled to a spontan eous strain along the c-axis. Structure analysis of the undistorted hi gh temperature T'-phase in Gd2CuO4 indicates persisting local distorti ons.