Mn local moments prevent superconductivity in iron-pnictides Ba(Fe 1-x Mn x)2As2

TL;DR

This study uses 75As NMR to show that Mn introduces local magnetic moments in Ba(Fe1-xMnx)2As2, which prevents superconductivity by causing magnetic scattering, unlike other dopants.

Contribution

It provides direct NMR evidence that Mn creates local magnetic moments and does not induce charge doping, explaining its suppression of superconductivity in iron-pnictides.

Findings

Mn carries a local magnetic moment in Ba(Fe1-xMnx)2As2.

Mn does not induce charge doping in the Fe layer.

Mn presence leads to magnetic scattering that prevents superconductivity.

Abstract

75As nuclear magnetic resonance (NMR) experiments were performed on Ba(Fe1-xMnx)2As2 (xMn = 2.5%, 5% and 12%) single crystals. The Fe layer magnetic susceptibility far from Mn atoms is probed by the75As NMR line shift and is found similar to that of BaFe2As2, implying that Mn does not induce charge doping. A satellite line associated with the Mn nearest neighbours (n.n.) of 75As displays a Curie-Weiss shift which demonstrates that Mn carries a local magnetic moment. This is confirmed by the main line broadening typical of a RKKY-like Mn-induced staggered spin polarization. The Mn moment is due to the localization of the additional Mn hole. These findings explain why Mn does not induce superconductivity in the pnictides contrary to other dopants such as Co, Ni, Ru or K.