Thermal conductivity of the quasi one-dimensional spin system Sr ₂V₃O₉

We have measured the thermal conductivity along the [101] direction, κ_[101], along the [101̄] direction, κ _[101̄], and along the b-axis, κ_b, of the quasi one-dimensional S=1/2 spin system Sr₂V₃O₉ in magnetic fields up to 14 T, in order to find the thermal conductivity due to spinons and to clarify whether the spin-chains run along the [101] or [101̄] direction. It has been found that both κ_[101], kappa;_[101̄] and κ_b show one peak around 10 K in zero field and that the magnitude of κ_[101̄] is larger than those of κ_[101] and kappa;_b. By the application of magnetic field along the heat current, the peak of kappa; _[101̄] is markedly suppressed, while the peaks of κ_[101] and K_b little change. These results indicate that there is a large contribution of spinons to κ_[101̄] and suggest that the spin-chains run along the [101̄] direction.