Frandsen, Benjamin A.Taddei, Keith M.Yi, MingFrano, AlexGuguchia, ZurabYu, RongSi, QimiaoBugaris, Daniel E.Stadel, RyanOsborn, RaymondRosenkranz, StephanChmaissem, OmarBirgeneau, Robert J.2018-06-272018-06-272017Frandsen, Benjamin A., Taddei, Keith M., Yi, Ming, et al.. "Local Orthorhombicity in the Magnetic ${C}_{4}$ Phase of the Hole-Doped Iron-Arsenide Superconductor ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$." <i>Physical Review Letters,</i> 119, no. 18 (2017) American Physical Society: https://doi.org/10.1103/PhysRevLett.119.187001.https://hdl.handle.net/1911/102280We report on temperature-dependent pair distribution function measurements of Sr1−xNaxFe2As2, an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C4 phase. Quantitative refinements indicate that the instantaneous local structure in the C4 phase comprises fluctuating orthorhombic regions with a length scale of ∼2 nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. These results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C4 phase and the neighboring C2 and superconducting phases.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlePhysRevLett.119.187001https://doi.org/10.1103/PhysRevLett.119.187001