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.