Heat Transport Due to Two-Dimensional Magnon in K₂CuF₄

Abstract

The heat transport phenomenon in the two-dimensional Heisenberg ferromagnet K₂CuF₄ in investigated through the measurement of thermal conductivity under the magnetic field. The evidence and the quantitative estimation to magnon conductivity are obtained below the ordering temperature T_c. In the vicinity of T_c the anomalous dip of the conductivity, representing the phonon scattering by the critical fluctuation of spins, is observed. Above T_c, the enhanced conduction is also found, which is attributed to the diffusion or paramagnetic magnon.