Constraints on magnetism and correlations in RuO$_2$ from lattice dynamics and M\"ossbauer spectroscopy

TL;DR

This study combines experimental techniques and theoretical calculations to demonstrate that bulk RuO$_2$ lacks a magnetic moment and that electronic correlations, not magnetic order, primarily influence its lattice dynamics.

Contribution

It provides comprehensive experimental and theoretical evidence showing the absence of magnetism in RuO$_2$ and highlights the importance of electronic correlations in its lattice behavior.

Findings

Negligible magnetic hyperfine splitting in RuO$_2$

Electronic correlations dominate lattice dynamics

No evidence of magnetic order in bulk RuO$_2"

Abstract

We provide experimental evidence for the absence of a magnetic moment in bulk RuO$_2$, a candidate altermagnetic material, by using a combination of M\"ossbauer spectroscopy, nuclear forward scattering, inelastic X-ray and neutron scattering, and density functional theory calculations. Using complementary M\"ossbauer and nuclear forward scattering we determine the $^{99}$Ru magnetic hyperfine splitting to be negligible. Inelastic X-ray and neutron scattering derived lattice dynamics of RuO$_2$ are compared to density functional theory calculations of varying flavors. Comparisons among theory with experiments indicate that electronic correlations, rather than magnetic order, are key in describing the lattice dynamics.