Formation and Control of Twin Domains in the Pyrochlore Oxide Cd2Re2O7

TL;DR

This study investigates the formation and control of twin domains in Cd2Re2O7 during its phase transitions, revealing domain pattern changes and magnetic susceptibility anisotropy reversals at specific transition temperatures.

Contribution

It provides detailed visualization and analysis of twin domain behavior and magnetic anisotropy changes across phase transitions in Cd2Re2O7, a pyrochlore oxide.

Findings

Twin domains form during the cubic-to-tetragonal transition at Ts1 ~ 200 K.

A dramatic change in twinning pattern occurs at Ts2 ~ 120 K, indicating a c-axis flip.

Magnetic susceptibility anisotropy reverses at Ts2, with ~10% anisotropy observed.

Abstract

The successive phase transitions of the pyrochlore oxide Cd2Re2O7 are studied by polarizing microscopy and magnetic susceptibility measurements. The formation of twin domains is visualized in the polarizing images of a pristine (111) crystal surface upon cooling through the cubic-to-tetragonal transition at Ts1 ~ 200 K. Moreover, a dramatic change in the twinning pattern is observed at Ts2 ~120 K, which suggests that the tetragonal c axis flips as the strain changes its direction at the tetragonal-to-tetragonal transition. Magnetic susceptibility measurements reveal significant domain alignment upon cooling across Ts1 and Ts2 in a magnetic field of 7 T, which are due to ~10% anisotropy in the magnetic susceptibility for the low-temperature phases. Interestingly, the anisotropy is reversed at Ts2: \c{hi}c < \c{hi}a above Ts2 and vice versa below Ts2.