High-Energy Spin Dynamics in La$_{1.69}$Sr$_{0.31}$NiO$_4$

TL;DR

This study maps high-energy spin excitations in a stripe-ordered nickelate using neutron scattering, revealing isotropic spin-wave velocities similar to the parent compound and comparing these dynamics to high-$T_c$ cuprates.

Contribution

It provides detailed measurements of spin dynamics in La$_{1.69}$Sr$_{0.31}$NiO$_4$, highlighting similarities with undoped compounds and insights into magnetic excitations in stripe-ordered nickelates.

Findings

Spin-wave excitations up to 80 meV observed

Isotropic spin-velocity similar to parent compound

Comparison with high-$T_c$ cuprates discussed

Abstract

We have mapped out the spin dynamics in a stripe-ordered nickelate, La$_{2-x}$Sr$_{x}$NiO$_{4}$ with $x \simeq 0.31$, using inelastic neutron scattering. We observe spin-wave excitations up to 80 meV emerging from the incommensurate magnetic peaks with an almost isotropic spin-velocity: $\hbar c_s\sim 0.32$ eV \AA, very similar to the velocity in the undoped, insulating parent compound, La$_{2}$NiO$_{4}$. We also discuss the similarities and differences of the inferred spin-excitation spectrum with those reported in superconducting high-$T_c$ cuprates.