Evolution of the magnetic excitations in NaOsO$_3$ through its metal-insulator transition

TL;DR

This study investigates how magnetic excitations in NaOsO₃ evolve across its metal-insulator transition using RIXS, revealing a transition from well-defined magnons to a broad continuum indicative of magnetic fluctuations.

Contribution

It provides the first detailed observation of the continuous evolution of magnetic excitations through the MIT in NaOsO₃, linking itinerant and localized magnetic behaviors.

Findings

Magnons weaken and dampen approaching the metallic state

A broad continuum of excitations develops near the transition

Magnetic fluctuations resemble a nearly antiferromagnetic Fermi liquid

Abstract

The temperature dependence of the excitation spectrum in NaOsO$_{\text{3}}$ through its metal-to-insulator transition (MIT) at 410 K has been investigated using resonant inelastic X-ray scattering (RIXS) at the Os L$_{\text{3}}$ edge. High resolution ($\Delta E \sim$ 56 meV) measurements show that the well-defined, low energy magnons in the insulating state weaken and dampen upon approaching the metallic state. Concomitantly, a broad continuum of excitations develops which is well described by the magnetic fluctuations of a nearly antiferromagnetic Fermi liquid. By revealing the continuous evolution of the magnetic quasiparticle spectrum as it changes its character from itinerant to localized, our results provide unprecedented insight into the nature of the MIT in NaOsO$_{\text{3}}$.