The centrifugal Jahn-Teller effect in rare-earth cage systems

TL;DR

This paper explores how the Jahn-Teller effect manifests in rare-earth cage systems, revealing unique low-temperature behaviors such as ion displacement, entropy reduction, and increased multipolar susceptibilities, impacting the understanding of these materials.

Contribution

It introduces a specific Jahn-Teller effect in cage-type compounds with orbital degeneracy, extending the Crystalline Electric Field theory to account for ion displacement effects.

Findings

Ion distribution spreads inside the cage at low temperatures

Magnetic entropy is reduced in the paramagnetic range

Cage multipolar susceptibilities are increased

Abstract

The analysis of the properties of rare-earth based materials relies on the Crystalline Electric Field theory. This theory has to be reconsidered in case of cage-type compounds, where the rare-earth ion can substantially depart from its, high symmetry, average position. It is shown that, in case of an orbital degeneracy at the cage center, a specific Jahn-Teller effect develops in the paramagnetic range: at low temperature, the distribution of the magnetic ion spreads inside the cage, the magnetic entropy is reduced, whereas the cage multipolar susceptibilities are increased. These consequences are put in relation with the properties of some metallic rare-earth cage compounds.