Magnon-mediated thermal conductivity in the dimerized spin-gap compound BaCu2 V2 O8

We have measured the thermal conductivity (κ) of the quasi-one-dimensional spin-gap compound BaCu2 V2 O8 with heat flow parallel and perpendicular to the chain axis. Distinctive differences in the magnitude and temperature dependence between these directions have been observed. A weak but non-negligible contribution to κ along the chain has been identified, attributed to the magnon heat transport. An analysis using a simple kinetic approach has been employed to rationalize this contribution. We also estimated the temperature dependent mean-free path for the magnon scattering. The result implies that the magnon-phonon scattering is a major process for the magnon-assisted κ at intermediate temperatures.