Large magnetothermal effect and spin-phonon coupling in a parent insulating cuprate Pr1.3La0.7CuO4

The magnetic-field (H) dependence of the thermal conductivity kappa of Pr1.3La0.7CuO4 is found to show a pronounced minimum for in-plane fields at low temperature, which is best attributed to the scattering of phonons by free spins that are seen by a Schottky-type specific heat and a Curie-Weiss susceptibility. Besides pointing to a strong spin-phonon coupling in cuprates, the present result demonstrates that the H dependence of the phonon heat transport should not be naively neglected when discussing the kappa(H) behavior of cuprates, since the Schottky anomaly is ubiquitously found in cuprates at any doping.