The influence of the magnetic subsystem on the heat transport in CsMnCl₃ · 2H₂O

Abstract

The thermal conductivity of CsMnCl 3 Á 2H 2 O (CMC) -a quasione-dimensional antiferromagnet with spin 5/2 has been studied in the temperature range from 2 to 25 K in zero magnetic field. The analysis of the data performed within Debye model revealed the combined effect of the single-ion and volume magnetostriction in the vicinity of a phase transition. Thermal-conductivity calculations based on the model and corresponding experimental studies showed that the poor sample quality and small dimensions can suppress the manifestation of a spin-phonon coupling present in CMC.1 Introduction Recent studies of low-dimensional spin systems revealed anomalous thermal transport that can be attributed to magnetic excitations providing an additional heat channel to the system. A large magnetic contribution to the thermal conductivity has been indicated in the S ¼ 1/2 Heisenberg chain Sr 2 CuO 3 , in spin-ladder materials (Ca, La, Sr) 14 Cu 24 O 41 , as well as in the twodimensional Nd 2 CuO 4 and Sr 2 CuO 2 Cl 2 systems [1][2][3][4]. All these materials are characterized by a strong magnetic interaction J/k B % 1000-2000 K, giving rise to a large group magnon velocity related to the magnetic Debye temperature Q m % J/k B , which is much higher than the phonon Debye temperature Q D . The magnon subsystem itself is able to transport heat effectively even at the temperatures where the intensive phonon umklapp scattering significantly reduces the heat transport via a phonon channel. On the other hand, in the systems with a weak magnetic interaction, Q m ( Q D , magnons can be excited over the whole Brillouin zone even at helium temperatures where the phonon channel for the heat transport is strongly suppressed