Low-temperature structural transition in FeCr_2S_4

TL;DR

This study investigates the low-temperature structural transition in FeCr_2S_4, revealing a symmetry reduction from cubic to triclinic, driven by Jahn-Teller and trigonal distortions, using transmission electron microscopy.

Contribution

It provides detailed experimental evidence of the cubic-to-triclinic transition and identifies the combined distortions responsible for the symmetry change in FeCr_2S_4.

Findings

Structural transition from Fd3m to F-43m symmetry.

Cubic-to-triclinic symmetry reduction at low temperatures.

Distortions caused by Jahn-Teller active Fe^2+ and Cr^3+ ion displacements.

Abstract

Transmission electron microscopy studies of [110] and [111] oriented FeCr_2S_4 single crystals at different temperatures reveal a structural transition at low temperatures indicating a cubic-to-triclinic symmetry reduction within crystallographic domains. The overall crystal symmetry was found to be reduced from Fd3m to F-43m. The triclinic distortions were suggested to result from the combined actions of tetragonal distortions due to the Jahn-Teller active Fe^2+ ions and trigonal distortions due to a displacement of the Cr^3+ ions in the <111> direction.