Magnetic interactions in iron superconductors: A review

TL;DR

This review discusses the complex magnetic interactions in iron-based superconductors, emphasizing the role of orbital physics, Hund's coupling, and various theoretical models in understanding their magnetic and superconducting properties.

Contribution

It unifies multiple mechanisms explaining magnetic order in iron superconductors through a comprehensive phase diagram incorporating orbital degrees of freedom.

Findings

Orbital physics is key to understanding magnetic softness and anisotropies.

Theoretical models align with experimental data to locate Fe superconductors in the phase diagram.

Multiple mechanisms can explain (,0) magnetic order in iron pnictides.

Abstract

High temperature superconductivity in iron pnictides and chalcogenides emerges when a magnetic phase is suppressed. The multi-orbital character and the strength of correlations underlie this complex phenomenology, involving magnetic softness and anisotropies, with Hund's coupling playing an important role. We review here the different theoretical approaches used to describe the magnetic interactions in these systems. We show that taking into account the orbital degree of freedom allows us to unify in a single phase diagram the main mechanisms proposed to explain the (\pi,0) order in iron pnictides: the nesting-driven, the exchange between localized spins, and the Hund induced magnetic state with orbital differentiation. Comparison of theoretical estimates and experimental results helps locate the Fe superconductors in the phase diagram. In addition, orbital physics is crucial to address the magnetic softness, the doping dependent properties, and the anisotropies.