Search

The magnetic properties of KUO 3 with the cubic perovskite structure have been studied. It shows an antiferromagnetic-type of transition at ca. 17 K in the magnetic susceptibility vs. temperature curve. Magnetic hysteresis is observed at 4.5 K, but not observed at 20 K. Neutron diffraction measurements have been performed on the powdered KUO 3 below and above the transition temperature. The neutron diffraction pattern measured at 10 K shows no appreciable difference from that measured at 50 K. A small ordered magnetic moment of U 5+ ion will make it very difficult to observe magnetic diffractions, even if a magnetic ordering occurs. If the magnetic spin alignment occurs in a small domain, no magnetic diffraction will be found in the neutron experiments. On the other hand, the magnetic phenomena of KUO 3 have been analyzed on the basis of an octahedral crystal field model.

The crystal structure of orthorhombic TlSr 2 CuO y was determined by Rietveld analysis of neutron powder diffraction data with the aid of electron diffraction and high-resolution electron microscopy. We found that oxygen vacancies are formed along the a -direction in a CuO 2− z sheet, which is consistent with a superstructure of twice the subcell along the b -direction. CuO 6 octahedra and CuO 4 square planes alternate along the b -direction by sharing their corners in accordance with the ordered oxygen vacancies in the CuO 2− z sheet. An apical oxygen atom in the CuO 6 octahedron is nearer to a TlO layer than an oxygen atom shared by a TlO 6 octahedron and the CuO 4 plane. A crystal-structure image obtained by high-resolution electron microscopy could be successfully reproduced by computer simulation using structure parameters obtained by neutron powder diffraction.

The magnetic properties of KUO 3 with the cubic perovskite structure have been studied. It shows an antiferromagnetic-type of transition at ca. 17 K in the magnetic susceptibility vs. temperature curve. Magnetic hysteresis is observed at 4.5 K, but not observed at 20 K. Neutron diffraction measurements have been performed on the powdered KUO 3 below and above the transition temperature. The neutron diffraction pattern measured at 10 K shows no appreciable difference from that measured at 50 K. A small ordered magnetic moment of U 5+ ion will make it very difficult to observe magnetic diffractions, even if a magnetic ordering occurs. If the magnetic spin alignment occurs in a small domain, no magnetic diffraction will be found in the neutron experiments. On the other hand, the magnetic phenomena of KUO 3 have been analyzed on the basis of an octahedral crystal field model.