Anomalous magnetic phase in an undistorted pyrochlore oxide Cd2Os2O7 induced by geometrical frustration

TL;DR

This study investigates the magnetic properties of undistorted Cd2Os2O7, revealing a transition from strong spin fluctuations to a static spin density wave, driven by geometrical frustration in a pyrochlore structure.

Contribution

It provides new insights into the magnetic phase transition and spin dynamics in undistorted pyrochlore oxides induced by geometrical frustration.

Findings

Strong spin fluctuations observed below the metal-insulator transition.

Discontinuous development of a static spin density wave below 150 K.

Evidence of an anomalous magnetic transition without structural change.

Abstract

We report on the muon spin rotation/relaxation study of a pyrochlore oxide, Cd2Os2O7, which exhibits a metal-insulator (MI) transition at T_{MI}~225 K without structural phase transition. It reveals strong spin fluctuation (>10^8/s) below the MI transition, suggesting a predominant role of geometrical spin frustration amongst Os^{5+} ions. Meanwhile, upon further cooling, a static spin density wave discontinuously develops below T_{SDW}~150 K. These observations strongly suggest the occurrence of an anomalous magnetic transition and associated change in the local spin dynamics in undistorted pyrochlore antiferromagnet.