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.Comment: 5 pages, 4 figure
