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 [1], the presence of diffuse and weakly temperature dependent magnetic (π,π) checkerboard scattering [2], and an apparent absent structural distortion from tetragonal to orthorhombic [3]. 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 [4]. 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 [5]. In this respect Mn exhibits a poisoning effect for the superconducting order.

 

[1] D. S. Inosov et al., Phys. Rev. B 87, 224425 (2013)

[2] G. S. Tucker et al., Phys. Rev. B 86, 020503(R) (2012)

[3] M. G. Kim et al., Phys. Rev. B 82, 220503(R) (2010)

[4] Maria N. Gastiasoro et al., submitted to Phys. Rev. Lett.

[5] F. Hammerath et al., Phys. Rev. B 89, 134503 (2014)

 

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