Low-temperature heat transport of Nd_2CuO_4: Roles of Nd magnons and spin-structure transitions

TL;DR

This study investigates how Nd magnons and spin-structure transitions influence low-temperature heat transport in Nd_2CuO_4, revealing their dual role as heat carriers and phonon scatterers depending on magnetic states.

Contribution

It uncovers the dual role of Nd^{3+} magnons in heat transport and their dependence on magnetic transitions in Nd_2CuO_4 at very low temperatures.

Findings

Nd magnons can transport heat in the spin-flopped state.

Magnetic scattering of phonons is affected by magnetic transitions.

High magnetic fields suppress magnon transport and scattering.

Abstract

We report the magnetic-field dependence of thermal conductivity (\kappa) of an insulating cuprate Nd_2CuO_4 at very low temperatures down to 0.3 K. It is found that apart from the paramagnetic moments scattering on phonons, the Nd^{3+} magnons can act as either heat carriers or phonon scatterers, which strongly depends on the long-range antiferromagnetic transition and the field-induced transitions of spin structure. In particular, the Nd^{3+} magnons can effectively transport heat in the spin-flopped state of the Nd^{3+} sublattice. However, both the magnon transport and the magnetic scattering are quenched at very high fields. The spin re-orientations under the in-plane field can be conjectured from the detailed field dependence of \kappa.