Resonant scattering of phonons in the quasi-one-dimensional spin-chain compounds AB2O6 ( A = Ni, Co; B

Abstract

We report measurements of thermal conductivity (κ) on single crystals of the quasi-onedimensional antiferromagnetic spin-chain compounds, AB2O6 (A=Ni, Co; B=Sb, Ta) in the temperature range 5K ≤ T ≤ 300K. 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.

Significant magneto-elastic coupling at Griffiths-like phase boundaries in low dimensional oxides, ASb2O6 (A = Ni and Mn)

“…As illustrated in Fig. 1(b), the dominant super-exchange paths (Ni-O-O-Ni) form the one-dimensional (1D) chains along [110] and [110] directions at z = 0 and 1/2, respectively [33,34]. A quasi-1D AFM order was proposed for NSO using the neutron diffraction studies [35,36], pointing an AFM ordering temperature (T N ) at 6.7 K [37].…”

“…Here, Θ CW is the PM Curie-Weiss (CW) temperature. These systems have been revisited focusing on different issues of the long range AFM states, proposing a possible occurrence of the short range magnetic ordering above T N for NSO [34,35,37] and MSO [38,40,41,43], which was attributed to the low dimensionality. However, the proper characterization of the short range ordered magnetic states has not been attempted so far for both the compounds.…”

Signatures of low-dimensional magnetism and short-range magnetic order in Co-based trirutiles

“…A similar decrease in intensity is observed for the Raman peak at 465 cm −1 without a frequency shift. Comparison of the intensity of this vibrational line in the Raman spectrum of CoTa 2 O 6 with its intensity in the spectrum of MgTa 2 O 6 reveals that the observed pattern in intensity changes in the Co 18 . It is worth noting that the thermal conductivity of our CoTa 2 O 6 sample could be reduced due to the porosity that might be present in the material.…”

“…The value for T N observed in κ(T ) is similar to the value observed in C p (T ). Recent detailed work on the thermal conductivity of CoTa 2 O 6 and CoSb 2 O 6 single crystals showed that the Ta compounds have lower values of κ(T ) compared to the Sb counterparts 18 . It is worth noting that the thermal conductivity of our CoTa 2 O 6 sample could be reduced due to the porosity that might be present in the material.…”

“…An anisotropic magnetocaloric effect has been reported in NiTa 2 O 6 12 . Spin-phonon interactions and their signatures in low-dimensional magnetic systems were recently probed in the case of M T 2 O 6 (M = Ni, Co; T = Ta, Sb) 18 . Significant reduction in the thermal conductivity of the Ta-based compounds was observed compared to that of the Sb-based systems.…”