Tetrahedral Magnetic Order and the Metal-Insulator Transition in the Pyrochlore Lattice of Cd2Os2O7

TL;DR

This paper investigates the magnetic structure and transition mechanism in Cd2Os2O7, revealing a noncollinear all-in/all-out magnetic order and proposing an alternative to the Slater mechanism for its metal-insulator transition.

Contribution

It uncovers the magnetic structure in Cd2Os2O7 and suggests a new transition mechanism involving tetrahedral magnetic order and spin-orbit interactions.

Findings

Identified a noncollinear all-in/all-out magnetic order.

Confirmed the transition occurs without spatial symmetry breaking.

Proposed an alternative transition mechanism beyond the Slater model.

Abstract

Cd2Os2O7 shows a peculiar metal-insulator transition at 227 K with magnetic ordering in a frustrated pyrochlore lattice, but its magnetic structure in the ordered state and the transition origin are yet uncovered. We observed a commensurate magnetic peak by resonant x-ray scattering in a high-quality single crystal. X-ray diffraction and Raman scattering experiments confirmed that the transition is not accompanied with any spatial symmetry breaking. We propose a noncollinear all-in/all-out spin arrangement on the tetrahedral network made of Os atoms. Based on this we suggest that the transition is not caused by Slater mechanism as believed earlier but by an alternative mechanism related to the formation of the specific tetrahedral magnetic order on the pyrochlore lattice in the presence of strong spin-orbit interactions.