We present a 75As Nuclear Magnetic Resonance (NMR) and resistivity study  of the effect of 5.5 MeV proton irradiation on the optimal electron doped (x = 0.068) and overdoped (x = 0.107) Ba(Fe1−xRhx)2As2 iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual resistivity [1,2] in both compositions, sizable broadening of the NMR spectra was observed in the optimally doped samples (x=0.068) at low temperature. The Curie Weiss temperature dependence of the line width suggests the onset of ferromagnetic correlations coexisting with superconductivity at the nanoscale. The effect is absent in the overdoped sample owing to the absence of significant spin correlations. Futhermore spin-spin relaxation rate (1/T2) measurements revealed that the low-frequency fluctuations observed in several families of iron-based superconductors [3,4], and whose nature is presently subject of debate, are damped by the irradiation induced impurities, consistently with the hypothesis that they could be associated with the presence of nematic fluctuations between (0, π) and (π,0) nematic phases.
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