Low-temperature structural change and magnetic anomaly in superconducting Cd2Re2O7 -: art. no. 100509

The structural phase transition at T(*)similar to200 K in the superconducting pyrochlore oxide Cd2Re2O7 has been investigated using x-ray and electron diffraction experiments and Cd-111-NMR (nuclear-magnetic-resonance) measurements. The susceptibility for Cd2Re2O7 in the high-temperature region (T>T-*) obeys a Curie-Weiss law with a large and negative Weiss temperature, which indicates that this system possesses a localized-moment nature with antiferromagnetic interactions, leading to geometrical frustration. X-ray and electron-diffraction measurements suggest the tetramerization of Re below T-*, which induces a nanosized stripe structure. From Cd-111-NMR experiments, a large orbital susceptibility is identified by means of a K-chi plot. Both the spin susceptibility and (T1T)(-1) are found to decrease sharply below T-*, signaling a decrease in density of states, which is apparently caused by a developing partial energy gap at the Fermi surface.