Orbital Freezing in FeCr2S4 Studied by Dielectric Spectroscopy

TL;DR

This study uses dielectric spectroscopy to investigate orbital transitions in FeCr2S4, revealing a transition to an orbital glass phase and characterizing the dynamics of orbital freezing.

Contribution

It provides the first detailed dielectric analysis of orbital glass transition and relaxation dynamics in FeCr2S4, including quantum tunneling effects at low temperatures.

Findings

Identification of orbital glass transition via dielectric permittivity.

Observation of slow orbital relaxation dynamics over six decades.

Suppression of glass transition at lowest temperatures due to quantum tunneling.

Abstract

Broadband dielectric spectroscopy has been performed on single-crystalline FeCr2S4 revealing a transition into a low-temperature orbital glass phase and on polycrystalline FeCr2S4 where long-range orbital order is established via a cooperative Jahn-Teller transition. The freezing of the orbital moments is revealed by a clear relaxational behavior of the dielectric permittivity, which allows a unique characterization of the orbital glass transition. The orbital relaxation dynamics continuously slows down over six decades in time, before at the lowest temperatures the glass transition becomes suppressed by quantum tunneling.