Heat transport of the quasi-one-dimensional alternating spin chain material (CH_{3})_{2}NH_{2}CuCl_{3}

We report a study of the low-temperature heat transport in the quasi-one-dimensional S = 1/2 alternating antiferromagnetic-ferromagnetic chain compound (CH_{3})_{2}NH_{2}CuCl_{3}. Both the temperature and magnetic-field dependencies of thermal conductivity are very complicated, pointing to the important role of spin excitations. It is found that magnetic excitations act mainly as the phonon scatterers in a broad temperature region from 0.3 to 30 K. In magnetic fields, the thermal conductivity show drastic changes, particularly at the field-induced transitions from the low-field N{e}el state to the spin-gapped state, the field-induced magnetic ordered state, and the spin polarized state. In high fields, the phonon conductivity is significantly enhanced because of the weakening of spin fluctuations.

Low-temperature heat transport of the layered spin-dimer compound Ba_3Mn_2O_8

We report the study on the low-temperature heat transport of Ba_3Mn_2O_8 single crystal, a layered spin-dimer compound exhibiting the magnetic-field-induced magnetic order or the magnon Bose-Einstein condensation. The thermal conductivities (kappa) along both the ab plane and the c axis show nearly isotropic dependence on magnetic field, that is, kappa is strongly suppressed with increasing field, particularly at the critical fields of magnetic phase transitions. These results indicate that the magnetic excitations play a role of scattering phonons and the scattering effect is enhanced when the magnetic field closes the gap in the spin spectrum. In addition, the magnons in the BEC state of this materials do not show notable ability of carrying heat.

Thermal conductivity of pure and Zn-doped LiCu_2O_2 single crystals

We report a study of the low-temperature thermal conductivity (kappa) of pure and Zn-doped LiCu_2O_2 single crystals. The kappa(T) of pure LiCu_2O_2 single crystal shows a double-peak behavior, with two peaks locating at 48 K and 14 K, respectively. The different dependences of the peaks on the Zn concentration indicate that the high-T peak is likely due to the phonon transport while the low-T one is attributed to the magnon transport in the spin spiral ordering state. In addition, the magnetic field can gradually suppress the low-T peak but does not affect the high-T one; this further confirms that the low-T peak is originated from the magnon heat transport.