Infrared phonons and specific heat in Ba3Cr2O8

TL;DR

This study investigates the phonon spectrum and specific heat of Ba3Cr2O8, revealing phonon mode splitting at the Jahn-Teller transition and analyzing the contributions of various degrees of freedom under magnetic fields.

Contribution

It provides new insights into the phonon behavior and the absence of orbital fluctuations in Ba3Cr2O8 compared to similar compounds.

Findings

Phonon modes split below T_{JT} = 70 K.

Specific heat analysis shows no orbital fluctuations below the transition.

Field-dependent specific heat data elucidates contributions from lattice, magnetic, and orbital degrees.

Abstract

We report on the phonon spectrum of Ba3Cr2O8 determined by infrared spectroscopy, and on specific heat measurements across the Jahn-Teller transition in magnetic fields up to 9 T. Phonon modes split below the Jahn-Teller transition, which occurs at T_{JT} = 70 K as detected by specific heat measurements. The field-dependent specific heat data is analyzed in terms of the contributions from lattice, magnetic and orbital degrees of freedom. In contrast to the isostructural compound Sr3Cr2O8 our analysis does not indicate the existence of orbital fluctuations below the Jahn-Teller transition in Ba3Cr2O8.