Low-temperature heat transport of the layered spin-dimer compound Ba_3Mn_2O_8

TL;DR

This study investigates how magnetic fields influence low-temperature heat transport in the layered spin-dimer compound Ba_3Mn_2O_8, revealing magnetic excitations significantly scatter phonons and magnons do not effectively carry heat in the BEC state.

Contribution

It provides new insights into the magnetic field dependence of thermal conductivity and the role of magnetic excitations in heat transport in Ba_3Mn_2O_8.

Findings

Thermal conductivity is strongly suppressed at magnetic phase transitions.

Magnetic excitations scatter phonons more effectively near critical fields.

Magnons in the BEC state do not carry heat notably.

Abstract

We report the study on the low-temperature heat transport of Ba_3Mn_2O_8 single crystal, a layered spin-dimer compound exhibiting the magnetic-field-induced magnetic order or the magnon Bose-Einstein condensation. The thermal conductivities (\kappa) along both the ab plane and the c axis show nearly isotropic dependence on magnetic field, that is, \kappa is strongly suppressed with increasing field, particularly at the critical fields of magnetic phase transitions. These results indicate that the magnetic excitations play a role of scattering phonons and the scattering effect is enhanced when the magnetic field closes the gap in the spin spectrum. In addition, the magnons in the BEC state of this materials do not show notable ability of carrying heat.