Non-conventional superconducting fluctuations in Ba(Fe1−xRhx)2As2 iron-based superconductors

We measured the static uniform spin susceptibility of Ba(Fe1-xRhx)2As2iron-based superconductors, over a broad range of doping (0.041x0.094) and magnetic fields. At small fields (H1kOe) we observed, above the transition temperature Tc, the occurrence of precursor diamagnetism, which is not ascribable to the Ginzburg-Landau theory. On the contrary, our data agree with a phase fluctuation model, which has been used to interpret a similar phenomenology occurring in the high-Tccuprate superconductors. Additionally, in the presence of strong fields, the unconventional fluctuating diamagnetism is suppressed, whereas Ginzburg-Landau fluctuations are found, in agreement with literature.