On the dual role of the d-electrons in iron-pnictides

TL;DR

This paper investigates how d-electrons in iron-pnictides simultaneously contribute to local magnetic moments and metallic conductivity, revealing that magnetic ordering is driven by RKKY interactions rather than Fermi surface nesting.

Contribution

It provides an exact calculation of the energy of local magnetic centers and demonstrates the dominant role of RKKY interactions in magnetic transitions in iron-pnictides.

Findings

Spin density wave transition is RKKY-driven.

Electrons scatter on randomly oriented moments in the paramagnetic phase.

Multi-band structure influences the energy spectrum and conductivity.

Abstract

In the stoichiometric Fe-pnictides the same d-electrons form the local moments and participate in the metallic conductivity. In the manuscript the emergence of the magnetic moments on the Fe-sites, their interaction with the itinerant electrons are studied in the paramagnetic phase at the different relations between the onsite Coulomb repulsion and the intraatomic Hund's exchange. The energy of the local center that is due to its interaction with the conduction electrons is calculated exactly. It is found that the spin density wave transition is controlled by the RKKY interactions between the centers rather than by the nesting mechanism. In the paramagnetic phase the electrons scatter on the randomly oriented moments. The calculated inverse mean free time provides the interpretation for few available experimental data on the conductivity. The multi-band structure of the energy spectrum in iron pnictides is taken into account.