On the possibility of excitonic magnetism in Ir double perovskites

TL;DR

This study investigates the potential for excitonic magnetism in Ir double perovskites using advanced computational methods, revealing they are insulators with large spin gaps that hinder magnetic ordering.

Contribution

The paper combines DFT, RPA, and many-body techniques to analyze the magnetic properties of Sr2YIRO6 and Ba2YIRO6, challenging previous experimental claims of excitonic magnetism.

Findings

Both materials are insulators with large spin gaps.

Large spin gaps prevent low-temperature magnetic ordering.

Contradicts earlier experimental suggestions of excitonic magnetism.

Abstract

We combine several numerical and semi-analytical methods to study the $5d$ double perovskites Sr2YIRO6 and Ba2YIRO6 which were recently proposed to exhibit excitonic magnetism. Starting from the density functional theory and constrained random phase approximation we construct effective multi-band Hubbard models. These are analyzed by means of static and dynamical mean-field theories and strong coupling expansion. We find both materials to be insulators, but, contrary to the experimental claims, with a large spin gap of several hundreds meV preventing formation of an ordered state at low temperature