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The role of magnetic excitations in the thermal conductivity of Cu2Te2O5Cl2 and Cu2Te2O5Br2

We present the thermal conductivity data of spin-tetrahedra copper-tellurides Cu2Te2O5Cl2 and Cu2Te2O5Br2. The thermal conductivity is enhanced in both compounds below magnetic ordering temperatures as observed in the ac-susceptibility measurements [1], with the larger enhancement in the case of Cl sample. For temperatures above the transition temperature, the suppression of the thermal conductivity is originated in a spin-phonon coupling which causes the resonance effects in the spin subsystem. In the case of Br sample, the result of our analysis supports the intertetrahedra mean-field coupling model [2]. The origin of the thermal conductivity enhancement below the transition temperature is not completely understood. It might be caused by the change of spin-phonon coupling constant ; in that case, one can conclude that the coupling is stronger on the Cl sample. The other explanation includes the heat conduction of magnon modes, which are observed by Raman scattering experiments [3]. [1] M. Prester et al., Phys. Rev. B 69 (2004) 024512. [2] C. Gros et al., Phys. Rev. B 67 (2003) 174405. [3] J. Jensen et al., Europhys. Lett. 64 (2003) 689.

nonelectronic thermal conductivity and heat-pulse propagation in solids including thermal waves; spin diffusion

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