Thermodynamic Properties of Ferromagnetic Mott- Insulators GaV4S8

TL;DR

This study investigates the magnetic and thermodynamic properties of GaV4S8, revealing structural and ferromagnetic transitions, and discusses the electronic excitations related to cluster degeneracy and Coulomb interactions.

Contribution

It provides new experimental data on GaV4S8's phase transitions and offers an explanation for its electronic excitations based on cluster degeneracy and Coulomb repulsion.

Findings

Structural transition at 42K

Ferromagnetic order at 12K

High density of low energy electronic excitations

Abstract

We present the results of the magnetic and specific heat measurements on V4 tetrahedral-cluster compound GaV4S8 between 2 to 300K. We find two transitions related to a structural change at 42K followed by ferromagnetic order at 12K on cooling. Remarkably similar properties were previously reported for the cluster compounds of Mo4. These compounds show an extremely high density of low energy excitations in their electronic properties. We explain this behavior in a cluster compound as due to the reduction of coulomb repulsion among electrons that occupy highly degenerate orbits of different clusters.