Jahn-Teller induced elastic constant changes in TmPO4

Abstract
Elastic constants C66 and C44 have been measured for TmPO4 from 4.2 to 300K. C66 shows evidence of strong Jahn-Teller coupling of Tm3+ electronic states to lattice strain but there is no cooperative phase transition. Theory previously developed to describe TbVO4 gives a very good description of the data for TmPO4.