Anomalous thermal conductivity across the structural transition in SmBaMn2O6 single crystals

Abstract

To understand whether the enhancement of thermal conductivity could take place at different types of phase transitions, we conduct thermal measurements in SmBaMn2O6 single crystals which have both structural and magnetic phase transitions. In SmBaMn2O6, successive phase transitions in charge, spin, and lattice degrees of freedoms take place at Tco1∼362 K, Tco2∼190 K, and TN∼175 K. An enhancement of thermal conductivity is only observed at the structural transition around Tco1 while it is absent at the structural transition around Tco2. One possible explanation is that the spin-phonon coupling in this material strongly modifies the phonon spectra and prevents the evolution of soft-phonon modes around the antiferromagnetic transition TN, which lies right below Tco2. Our study provides a way to look for enhanced thermal conductivity in materials where multiple phase transitions coexist.