Structure Analysis of Gd 2 CuO 4 : a New Modification of the T ' Phase

Abstract
Neutron diffraction on a single crystal of Gd2CuO4 shows a long-range superstructure of the T' phase. The oxygen squares surrounding the Cu sites are rotated around the c-axis (by an angle of 5.2° at room temperature) leading to a reduced orthorhombic symmetry (space group: Acam). The reported structural deformation can explain previous results (weak ferromagnetism and Mössbauer effect) and might help to explain the non-existence of superconductivity in Gd2−xCexCuO4.