Large Magnetoelastic Coupling in Pr$_{2}$CuO$_{4}$ Single Crystals

The in-plane thermal conductivity, $\kappa _{a}$, of insulating Pr$_{2}$CuO$_{4}$ was measured at low temperatures and in magnetic fields of up to 8 Tesla. At 5 K and 8 Tesla $\kappa _{a}$ increases by 50{\%} for H // \textbf{a}, and 300{\%} for H // \textbf{c}, relative to its value in zero magnetic field. This increase is most likely due to the ability of the magnetic field to mix the non-magnetic ground state of the Pr 4f crystal field level with the first excited crystal field level at 18 meV. The magnetic field produces a substantial magnetic moment at each Pr site as well as a significant change in the 4$f$ charge distribution. Either effect could significantly alter the heat conducted by acoustic phonons. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725.