Thermal conductivity due to magnons in high-quality single crystals of the two-leg spin-ladder system (Ca,Sr,La)14Cu24O41

In order to enhance the thermal conductivity due to magnons, κ magnon , in the two-leg spin-ladder system (Ca,Sr,La)14Cu24O41, we have grown the single crystals using raw materials with high purity and tried to improve the quality of the single crystals through the annealing in O 2 atmosphere. A large enhancement of κ magnon has been observed through the O2-annealing in Sr14Cu24O41, while there has been little change in κ magnon of Ca9La5Cu24O41 nor Sr9La5Cu24O41 in spite of the increase of the purity of the raw materials and the O2-annealing. It has been concluded that the extension of the mean free path of magnons is limited by the disorder of the atomic arrangement due to the mismatch between the (Ca,Sr,La) plane and the Cu2O3 spin-ladder plane in both Ca9La5Cu24O41 and Sr9La5Cu24O41 and that the removal of the disorder of the atomic arrangement in the spin-ladder plane is necessary for the enhancement of κ magnon in (Ca,Sr,La)14Cu24O41.