Magnetic structures and electronic properties of cubic-pyrochlore ruthenates from first principles

TL;DR

This study combines advanced theoretical methods to predict magnetic ground states and electronic properties of cubic-pyrochlore ruthenates, revealing the interplay of $d$- and $f$-orbital magnetism in strongly correlated systems.

Contribution

It introduces a novel combination of CMP theory, SDFT, cRPA, and DMFT to accurately describe magnetic and electronic properties of ruthenates.

Findings

CMP+SDFT successfully predicts magnetic ground states.

cRPA explains differences in screening effects.

Electronic properties are understood within DMFT framework.

Abstract

The magnetic ground states of $R_2$Ru$_2$O$_7$ and $A_2$Ru$_2$O$_7$ with $R=$ Pr, Gd, Ho, and Er, as well as $A=$ Ca, Cd are predicted devising a combination of the cluster-multipole (CMP) theory and spin-density-functional theory (SDFT). The strong electronic correlation effects are estimated by the constrained-random-phase approximation (cRPA) and taken into account within the dynamical-mean-field theory (DMFT). The target compounds feature $d$-orbital magnetism on Ru$^{4+}$ and Ru$^{5+}$ ions for $R$ and $A$, respectively, as well as $f$-orbital magnetism on the $R$ site, which leads to an intriguing interplay of magnetic interactions in a strongly correlated system. We find CMP+SDFT is capable of describing the magnetic ground states in these compounds. The cRPA captures a difference in the screening strength between $R_2$Ru$_2$O$_7$ and $A_2$Ru$_2$O$_7$ compounds, which leads to a qualitative and quantitative understanding of the electronic properties within DMFT.