Intraplanar Magnetic Excitations in Na0.5CoO2: An Inelastic Neutron Study

TL;DR

This study uses inelastic neutron scattering to explore magnetic excitations in Na0.5CoO2, revealing dispersive, itinerant magnetic excitations with a significant three-dimensional character and an energy gap of approximately 11.5 meV.

Contribution

It provides the first detailed mapping of in-plane magnetic excitations in Na0.5CoO2, highlighting their dispersive and itinerant nature and the three-dimensional magnetic correlations.

Findings

Dispersive magnetic excitations above 11.5 meV energy gap

Magnetic excitations are highly damped and disappear near 35 meV

Magnetic correlations are three-dimensional, influenced by c-axis dispersion

Abstract

Inelastic neutron scattering measurements mapping the in-plane magnetic interactions of Na0.5CoO2 reveal dispersive excitations at points above an energy gap Eg = 11.5(5) meV at the superstructural Bragg reflections. The excitations are highly damped, broadening with increasing energy, and disappear at hw ~ 35 meV, a strong indication that the magnetism is itinerant. Tilting into the ac plane reduces the value of Eg by 25%, suggesting that the dispersion along c is significant and the magnetic correlations are three-dimensional, as seen at the higher doping levels.