  The thermal conductivity of the spin-1/2 chain cuprate BaCu2Si2O7 was
measured along different crystallographic directions in the temperature region
between 0.5 and 300 K. The thermal conductivity along the chain direction
considerably exceeds that along perpendicular directions. Near the
antiferromagnetic transition at T_N = 9.2 K the data indicates enhanced
scattering of phonons by critical fluctuations in the spin system. A comparison
of the data above T_N with available results on similar materials reveals
similarities in the main features of the temperature dependence of the mean
free path of itinerant spin excitations. This universal behavior is most likely
caused by the spin-lattice interaction.
