Enhancement of Ferroelectricity for Orthorhombic (Tb<sub>0.861</sub>Mn<sub>0.121</sub>)MnO<sub>3−δ</sub> by Copper Doping

Copper-doped (Tb<sub>0.861</sub>Mn<sub>0.121</sub>)­MnO<sub>3−δ</sub> has been synthesized by the conventional solid state reaction method. X-ray, neutron, and electron diffraction data indicate that they crystallize in <i>Pnma</i> space group at room temperature. Two magnetic orderings are found for this series by neutron diffraction. One is the ICAM (incommensurate canted antiferromagnetic) ordering of Mn with a wave vector <i>q</i><sub>Mn</sub> = (∼0.283, 0, 0) with <i>a</i> ≈ 5.73 Å, <i>b</i> ≈ 5.31 Å, and <i>c</i> ≈ 7.41 Å, and the other is the CAM (canted antiferromagnetic) ordering of both Tb and Mn in the magnetic space group <i>Pn</i>′<i>a2</i><sub>1</sub>′ with <i>a</i> ≈ 5.73 Å, <i>b</i> ≈ 5.31 Å, and <i>c</i> ≈ 7.41 Å. A dielectric peak around 40 K is found for the samples doped with Cu, which is higher than that for orthorhombic TbMnO<sub>3</sub>.