Determination of local atomic displacements in CeO₁-xF_xBiS₂ system

We have used Bi and Ce L 3-edges extended x-ray absorption fine structure measurements to study local structure of CeO₁-xF_xBiS₂ system as a function of F-substitution. The local structure of both BiS₂ active layer and CeO₁-xF_x spacer layer changes systematically. The in-plane Bi-S1 distance decreases (ΔRmax∼0.08) and the out-of-plane Bi-S2 distance increases (ΔRmax∼0.12) with increasing F-content. On the other hand, the Ce-O/F distance increases (ΔRmax∼0.2) with a concomitant decrease of the Ce-S2 distance (ΔR_max∼0.15). Interestingly, the Bi-S1 distance is characterized by a large disorder that increases with F-content. The results provide useful information on the local atomic displacements in CeO₁-xF_xBiS₂, that should be important for the understanding of the coexistence of superconductivity and low temperature ferromagnetism in this system.