The high temperature Jahn-Teller transition in LaMn7O12

TL;DR

This study investigates the structural, magnetic, and electrical changes in LaMn7O12 across its high-temperature Jahn-Teller transition at 650 K, revealing polaronic conduction and altered magnetic behavior.

Contribution

It provides new insights into the effects of the Jahn-Teller transition on electrical conduction and magnetic properties in LaMn7O12, including the impact of thermal cycling.

Findings

Electrical conduction is polaronic, shifting from non-adiabatic to adiabatic at T_{JT}

Magnetic behavior is consistent with non-interacting Mn3+ ions below T_{JT}

Thermal cycling clarifies intrinsic magnetic response at lower temperatures

Abstract

A first order structural Jahn-Teller transition at T_{JT} = 650 K has been recently reported for the quadruple perovskite LaMn7O12 . We have carried out magnetization and transport measurements below and above T_{JT} in order to investigate the effect of the transition. Electrical conduction turns out to be polaronic, changing from non-adiabatic to adiabatic through the transition. Magnetic behavior can be described by non-interacting Mn3+ ions below T_{JT}, while above T_{JT} it is of questionable interpretation. The effect of thermal cycling on as grown samples of different purity degree also allowed us to clarify the intrinsic magnetic response of LaMn7O12 at lower temperatures.