Thermal transport of the frustrated spin-chain mineral linarite: Magnetic heat transport and strong spin-phonon scattering

Abstract

The mineral linarite (PbCuSO${}_4$(OH)${}_2$) forms a monoclinic structure where a sequence of Cu(OH)${}_2$ units forms a spin-$\frac{1}{2}$ chain. Competing ferromagnetic nearest-neighbor ($J_1$) and antiferromagnetic next-nearest-neighbor interactions ($J_2$) in this quasi-one-dimensional spin structure imply magnetic frustration and lead to magnetic ordering below $T_N=$2.8 K in a mutliferroic elliptical spin-spiral ground state. Upon the application of a magnetic field along the spin-chain direction, distinct magnetically ordered phases can be induced. We studied the thermal conductivity $\kappa$ in this material across the magnetic phase diagram as well as in the paramagnetic regime in the temperature ranges 0.07-1 K and 9-300 K. We found that in linarite the heat is carried mainly by phonons but shows a peculiar non-monotonic behavior in field. In particular, $\kappa$ is highly suppressed at the magnetic phase boundaries, indicative of strong scattering of the phonons off critical magnetic fluctuations. Even at temperatures far above the magnetically ordered phases, the phononic thermal conductivity is reduced due to scattering off magnetic fluctuations. The mean free path due to spin-phonon scattering ($l_{\text{spin-phonon}}$) was determined as function of temperature. A power law behavior was observed mainly above 0.5 K indicating the thermal activation of spin fluctuations. In the critical regime close to the saturation field, $l_{\text{spin-phonon}}$ shows a $1/T$ dependence. Furthermore, a magnon thermal transport channel was verified in the helical magnetic phase. We estimate a magnon mean free path which corresponds to about 1000 lattice spacings.

References in corpus (6)

• Evidence for Ballistic Thermal Conduction in the One-Dimensional S=1/2 Heisenberg Antiferromagnetic Spin System Sr2CuO3
• The dynamics of linarite: Observations of magnetic excitations
• The magnetic phase diagram of the frustrated spin chain compound linarite, PbCuSO${}_4$(OH)${}_2$, as seen by neutron diffraction and ${}^1$H-NMR
• Multiferroic phases of the frustrated quantum spin-chain compound linarite
• Thermal conductivity of pure and Zn-doped LiCu_2O_2 single crystals
• Electron spin resonance in spiral antiferromagnet linarite: theory and experiment

Cited by in corpus (3)

• Heat transport of the kagomé Heisenberg quantum spin liquid candidate YCu${}_3$(OH)${}_{6.5}$Br${}_{2.5}$: localized magnetic excitations and spin gap
• Phononic-magnetic dichotomy of the thermal Hall effect in the Kitaev-Heisenberg candidate material Na${}_2$Co${}_2$TeO${}_6$
• Low-energy spin excitations of the frustrated ferromagnetic $J_1$-$J_2$ chain material linarite, PbCuSO${}_4$(OH)${}_2$, in applied magnetic fields $\mathbf{H}\parallel b$ axis