Anomalous magnetic phase in an undistorted pyrochlore oxide CdOsO induced by geometrical frustration

Koda, Akihiro*; Kadono, Ryosuke*; Oishi, Kazuki; Saha, S. R.*; Higemoto, Wataru  ; Yonezawa, Shigeki*; Muraoka, Yuji*; Hiroi, Zenji*

We report on the muon spin relaxation study of a pyrochlore oxide, CdOsO, which exhibits a metal-insulator transition. It reveals strong spin fluctuation below the MI transition, suggesting a predominant role of geometrical spin frustration. Meanwhile, an incommensurate spin density wave discontinuously develops at lower temperature. These observations strongly suggest the occurrence of an anomalous magnetic transition and associated change in the local spin dynamics in undistorted pyrochlore antiferromagnet.