Site-selective Probe of Magnetic Excitations in Rare-earth Nickelates using Resonant Inelastic X-ray Scattering

TL;DR

This study uses high-resolution RIXS to investigate magnetic excitations in NdNiO$_3$, revealing site-dependent magnons and providing insights into the magnetic interactions in rare-earth nickelates.

Contribution

It demonstrates that RIXS can be used as a site-selective probe of magnetic excitations and elucidates the magnetic dynamics in NdNiO$_3$ with a detailed model.

Findings

Observation of well-defined magnons below magnetic transition temperature.

Magnetic spectra vary with incident photon energy due to local electronic configurations.

Magnetic ground state and excitations explained by competition between exchange interactions.

Abstract

We have used high-resolution resonant inelastic x-ray scattering (RIXS) to study a thin film of NdNiO$_3$, a compound whose unusual spin- and bond-ordered electronic ground state has been of long-standing interest. Below the magnetic ordering temperature, we observe well-defined collective magnon excitations along different high-symmetry directions in momentum space. The magnetic spectra depend strongly on the incident photon energy, which we attribute to RIXS coupling to different local electronic configurations of the expanded and compressed NiO$_6$ octahedra in the bond-ordered state. Both the noncollinear magnetic ground state and the observed site-dependent magnon excitations are well described by a model that assumes strong competition between the antiferromagnetic superexchange and ferromagnetic double-exchange interactions. Our study provides direct insight into the magnetic dynamics and exchange interactions of the rare-earth nickelates, and demonstrates that RIXS can serve as a site-selective probe of magnetism in these and other materials.