Workshop "NMR, µSR, Mössbauer spectroscopies in the study of Fe-based and other unconventional high-Tc superconductors"
Poisoning and antidote effects of magnetic impurities in iron pnictides
Brian M. Andersen, Niels Bohr Institutet Copenhagen, Denmark
Recent experimental studies have revealed several unexpected magnetic properties of Mn-doped BaFe2As2. These include extension of the stripe-like magnetic (π,0) phase to high temperatures above a critical Mn concentration only , the presence of diffuse and weakly temperature dependent magnetic (π,π) checkerboard scattering , and an apparent absent structural distortion from tetragonal to orthorhombic . Here, we study the effects of magnetic impurities both below and above the Nèel transition temperature within a real-space five-band model appropriate to the iron pnictides. We show how these experimental findings can be explained by a cooperative magnetic impurity behavior of the conduction electrons mediating the Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions between the magnetic impurities . Our results show that Mn acts as an antidote to the (π,0) magnetic order in Mn-doped Ba-122. On the other hand, in the presence of superconductivity, Mn impurities can severely destroy the superconducting order if the host material is close to a magnetic quantum critical point, in agreement with recent experimental studies . In this respect Mn exhibits a poisoning effect for the superconducting order.
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