The local structure of the BiS&lt;sub&gt;2&lt;/sub&gt; Layer in RE(O,F)BiS&lt;sub&gt;2&lt;/sub&gt; determined by in-plane polarized X-ray absorption measurements

Pugliese, G.M.; Tortora, L.; Paris, E.; Wakita, T.; Terashima, K.; Puri, A.; Nagao, M.; Higashinaka, R.; Matsuda, T.D.; Aoki, Y.; Yokoya, T.; Mizokawa, T.; Saini, N.L.

doi:10.3390/physchem1030019

The local structure of the BiS₂ Layer in RE(O,F)BiS₂ determined by in-plane polarized X-ray absorption measurements

Pugliese GM, Tortora L, Paris E, Wakita T, Terashima K, Puri A, Nagao M, Higashinaka R, Matsuda TD, Aoki Y, Yokoya T, Mizokawa T & Saini NL

Citation

Pugliese, G. M., Tortora, L., Paris, E., Wakita, T., Terashima, K., Puri, A., … Saini, N. L. (2021). The local structure of the BiS₂ Layer in RE(O,F)BiS₂ determined by in-plane polarized X-ray absorption measurements. Physchem, 1(3), 250-258. https://doi.org/10.3390/physchem1030019

Persistent URL https://www.dora.lib4ri.ch/psi/islandora/object/psi:60747

We have investigated the local structure of BiS₂-based layered materials by Bi L₃-edge extended X-ray absorption fine structure (EXAFS) measurements performed on single crystal samples with polarization of the X-ray beam parallel to the BiS₂ plane. The results confirm highly instable nature of BiS₂ layer, characterized by ferroelectric like distortions. The distortion amplitude, determined by the separation between the two in-plane (Bi-S1) bonds, is found to be highest in LaO_0.77F_0.23BiS₂ with ΔR∼0.26 Å and lowest in NdO_0.71F_0.29BiS₂ with ΔR∼0.13 Å. Among the systems with intrinsic doping, CeOBiS₂ shows smaller distortion (ΔR∼0.15 Å) than PrOBiS₂ (ΔR∼0.18 Å) while the highest distortion appears for EuFBiS₂ revealing ΔR∼0.22 Å. It appears that the distortion amplitude is controlled by the nature of the RE(O,F) spacer layer in the RE(O,F)BiS₂ structure. The X-ray absorption near edge structure (XANES) spectra, probing the local geometry, shows a spectral weight transfer that evolves systematically with the distortion amplitude in the BiS2-layer. The results provide a quantitative measurements of the local distortions in the instable BiS₂-layer with direct implication on the physical properties of these materials.