Resonant scattering of phonons in the quasi-one-dimensional spin-chain compounds AB₂ O₆ (A = Ni, Co; B = Sb, Ta)

We report measurements of thermal conductivity (κ) on single crystals of the quasi-one-dimensional antiferromagnetic spin-chain compounds AB₂O₆ (A = Ni, Co; B = Sb, Ta) in the temperature range 5≤T≤300 K. We find that κ for all crystallographic directions is substantially suppressed in the Ta compounds in comparison to those of the Sb compounds despite their very similar magnetic and crystallographic structures. The data are well described by resonant scattering of phonons from two-level systems, with energy splittings of ∼100-150 K and scattering strength an order of magnitude greater in the Ta compounds. We distinguish the effects of phonon-spin interactions from those related to changes in the low-energy phonon spectra caused by the different B-site ions.