A comparative study of ultra-low-temperature thermal conductivity of multiferroic orthoferrites RFeO3 (R = Gd and Dy)

Ultra-low-temperature thermal conductivity (kappa) of GdFeO3 and DyFeO3 single crystals is studied down to several tens of milli-Kelvin. It is found that the kappa is purely phononic and has strong magnetic-field dependence, indicating a strong spin-phonon coupling. Moreover, the low-T kappa (H) with H parallel to c showrather different behaviors in these two materials. In particular, the kappa of GdFeO3 can be strongly enhanced in several tesla field and becomes weakly field dependent in higher fields up to 14 T; whereas, the kappa of DyFeO3 is continuously suppressed with increasing field and does not show any signature of recovery at 14 T. The results can be well understood by the difference in the spin anisotropy of Gd3+ and Dy3+ ions. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).