Low-temperature structural change and magnetic anomaly in superconducting CdReO

Sakai, Hironori; Kato, Harukazu; Kambe, Shinsaku  ; Walstedt, R. E.; Ono, Hiroyuki*; Kato, Masaki*; Yoshimura, Kazuyoshi*; Matsuhata, Hirofumi*

The structural phase transition at 200 K in the superconducting pyrochlore oxide CdReO has been investigated using X-ray and electron diffraction experiments and Cd NMR measurements. The susceptibility for CdReO in the high temperature region () 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 , which induces a nano-sized stripe structure. From Cd NMR experiments, a large orbital susceptibility is identified by means of a - plot. Both the spin susceptibility and are found to decrease sharply below , signaling a decrease in density of states which is apparently caused by a developing partial energy gap at the Fermi surface.