Magnetic excitations of spin and orbital moments in cobalt oxide

TL;DR

This study investigates magnetic and phonon excitations in antiferromagnetic CoO using neutron scattering, revealing coupled spin and orbital fluctuations influenced by superexchange interactions.

Contribution

It provides detailed neutron scattering measurements of magnetic excitations in CoO, highlighting the role of coupled orbital and spin degrees of freedom in its magnetic behavior.

Findings

Multiple magnetic excitation modes identified.

Excitations linked to coupled orbital and spin fluctuations.

Bandwidth controlled by interionic superexchange.

Abstract

Magnetic and phonon excitations in the antiferromagnet CoO with an unquenched orbital angular momentum are studied by neutron scattering. Results of energy scans in several Brillouin zones in the (HHL) plane for energy transfers up to 16 THz are presented. The measurements were performed in the antiferromagnetic ordered state at 6 K (well below TN~290 K) as well as in the paramagnetic state at 450 K. Several magnetic excitation modes are identified from the dependence of their intensity on wavevector and temperature. Within a Hund's rule model the excitations correspond to fluctuations of coupled orbital and spin degrees of freedom whose bandwidth is controlled by interionic superexchange. The different <111> ordering domains give rise to several magnetic peaks at each wavevector transfer.